gdata: Move GDataWapiFeedLoader to a set of new files

This change reduces ~800 lines from gdata_file_system.cc
Along the way move some functions to gdata_util.h, which
are needed for gdata_file_system.cc and gdata_wapi_feed_loader.cc

BUG=138268
TEST=none; just move code around. should not change the behaviors
TBR=ben@chromium.org
for chrome_browser.gypi

Review URL: https://chromiumcodereview.appspot.com/10834170

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150027 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 1015 insertions, 948 deletions

diff --git a/chrome/browser/chromeos/gdata/gdata_file_system.cc b/chrome/browser/chromeos/gdata/gdata_file_system.cc
index ccffc8c..7de41a3 100644
--- a/chrome/browser/chromeos/gdata/gdata_file_system.cc
+++ b/chrome/browser/chromeos/gdata/gdata_file_system.cc
@@ -8,11 +8,8 @@
 #include <utility>
 
 #include "base/bind.h"
-#include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/json/json_file_value_serializer.h"
-#include "base/json/json_reader.h"
-#include "base/json/json_writer.h"
 #include "base/message_loop.h"
 #include "base/message_loop_proxy.h"
 #include "base/metrics/histogram.h"
@@ -28,7 +25,6 @@
 #include "chrome/browser/chromeos/gdata/gdata_util.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
-#include "chrome/common/chrome_switches.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
@@ -43,13 +39,6 @@ namespace {
 const char kMimeTypeJson[] = "application/json";
 const char kMimeTypeOctetStream[] = "application/octet-stream";
 
-const FilePath::CharType kAccountMetadataFile[] =
-    FILE_PATH_LITERAL("account_metadata.json");
-const FilePath::CharType kFilesystemProtoFile[] =
-    FILE_PATH_LITERAL("file_system.pb");
-const FilePath::CharType kResourceMetadataDBFile[] =
-    FILE_PATH_LITERAL("resource_metadata.db");
-
 const char kEmptyFilePath[] = "/dev/null";
 
 // GData update check interval (in seconds).
@@ -59,67 +48,6 @@ const int kGDataUpdateCheckIntervalInSec = 5;
 const int kGDataUpdateCheckIntervalInSec = 60;
 #endif
 
-// Update the fetch progress UI per every this number of feeds.
-const int kFetchUiUpdateStep = 10;
-
-// Schedule for dumping root file system proto buffers to disk depending its
-// total protobuffer size in MB.
-typedef struct {
-  double size;
-  int timeout;
-} SerializationTimetable;
-
-SerializationTimetable kSerializeTimetable[] = {
-#ifndef NDEBUG
-    {0.5, 0},    // Less than 0.5MB, dump immediately.
-    {-1,  1},    // Any size, dump if older than 1 minute.
-#else
-    {0.5, 0},    // Less than 0.5MB, dump immediately.
-    {1.0, 15},   // Less than 1.0MB, dump after 15 minutes.
-    {2.0, 30},
-    {4.0, 60},
-    {-1,  120},  // Any size, dump if older than 120 minutes.
-#endif
-};
-
-// Returns true if file system is due to be serialized on disk based on it
-// |serialized_size| and |last_serialized| timestamp.
-bool ShouldSerializeFileSystemNow(size_t serialized_size,
-                                  const base::Time& last_serialized) {
-  const double size_in_mb = serialized_size / 1048576.0;
-  const int last_proto_dump_in_min =
-      (base::Time::Now() - last_serialized).InMinutes();
-  for (size_t i = 0; i < arraysize(kSerializeTimetable); i++) {
-    if ((size_in_mb < kSerializeTimetable[i].size ||
-         kSerializeTimetable[i].size == -1) &&
-        last_proto_dump_in_min >= kSerializeTimetable[i].timeout) {
-      return true;
-    }
-  }
-  return false;
-}
-
-// Converts gdata error code into file platform error code.
-GDataFileError GDataToGDataFileError(GDataErrorCode status) {
-  switch (status) {
-    case HTTP_SUCCESS:
-    case HTTP_CREATED:
-      return GDATA_FILE_OK;
-    case HTTP_UNAUTHORIZED:
-    case HTTP_FORBIDDEN:
-      return GDATA_FILE_ERROR_ACCESS_DENIED;
-    case HTTP_NOT_FOUND:
-      return GDATA_FILE_ERROR_NOT_FOUND;
-    case GDATA_PARSE_ERROR:
-    case GDATA_FILE_ERROR:
-      return GDATA_FILE_ERROR_ABORT;
-    case GDATA_NO_CONNECTION:
-      return GDATA_FILE_ERROR_NO_CONNECTION;
-    default:
-      return GDATA_FILE_ERROR_FAILED;
-  }
-}
-
 //================================ Helper functions ============================
 
 // Invoked upon completion of TransferRegularFile initiated by Copy.
@@ -200,66 +128,6 @@ class InitialLoadObserver : public GDataFileSystemInterface::Observer {
   base::Closure callback_;
 };
 
-// Saves the string |serialized_proto| to a file at |path| on a blocking thread.
-void SaveProtoOnBlockingPool(const FilePath& path,
-                             scoped_ptr<std::string> serialized_proto) {
-  const int file_size = static_cast<int>(serialized_proto->length());
-  if (file_util::WriteFile(path, serialized_proto->data(), file_size) !=
-      file_size) {
-    LOG(WARNING) << "GData proto file can't be stored at "
-                 << path.value();
-    if (!file_util::Delete(path, true)) {
-      LOG(WARNING) << "GData proto file can't be deleted at "
-                   << path.value();
-    }
-  }
-}
-
-// Loads the file at |path| into the string |serialized_proto| on a blocking
-// thread.
-void LoadProtoOnBlockingPool(const FilePath& path,
-                             LoadRootFeedParams* params) {
-  base::PlatformFileInfo info;
-  if (!file_util::GetFileInfo(path, &info)) {
-    params->load_error = GDATA_FILE_ERROR_NOT_FOUND;
-    return;
-  }
-  params->last_modified = info.last_modified;
-  if (!file_util::ReadFileToString(path, &params->proto)) {
-    LOG(WARNING) << "Proto file not found at " << path.value();
-    params->load_error = GDATA_FILE_ERROR_NOT_FOUND;
-    return;
-  }
-  params->load_error = GDATA_FILE_OK;
-}
-
-// Saves json file content content in |feed| to |file_pathname| on blocking
-// pool. Used for debugging.
-void SaveFeedOnBlockingPoolForDebugging(
-    const FilePath& file_path,
-    scoped_ptr<base::Value> feed) {
-  std::string json;
-  base::JSONWriter::WriteWithOptions(feed.get(),
-                                     base::JSONWriter::OPTIONS_PRETTY_PRINT,
-                                     &json);
-
-  int file_size = static_cast<int>(json.length());
-  if (file_util::WriteFile(file_path, json.data(), file_size) != file_size) {
-    LOG(WARNING) << "GData metadata file can't be stored at "
-                 << file_path.value();
-    if (!file_util::Delete(file_path, true)) {
-      LOG(WARNING) << "GData metadata file can't be deleted at "
-                   << file_path.value();
-      return;
-    }
-  }
-}
-
-bool UseLevelDB() {
-  return CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kUseLevelDBForGData);
-}
-
 // Gets the file size of |local_file|.
 void GetLocalFileSizeOnBlockingPool(const FilePath& local_file,
                                     GDataFileError* error,
@@ -510,32 +378,6 @@ CallbackType CreateRelayCallback(const CallbackType& callback) {
                     callback);
 }
 
-// Wrapper around BrowserThread::PostTask to post a task to the blocking
-// pool with the given sequence token.
-void PostBlockingPoolSequencedTask(
-    const tracked_objects::Location& from_here,
-    base::SequencedTaskRunner* blocking_task_runner,
-    const base::Closure& task) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  const bool posted = blocking_task_runner->PostTask(from_here, task);
-  DCHECK(posted);
-}
-
-// Similar to PostBlockingPoolSequencedTask() but this one takes a reply
-// callback that runs on the calling thread.
-void PostBlockingPoolSequencedTaskAndReply(
-    const tracked_objects::Location& from_here,
-    base::SequencedTaskRunner* blocking_task_runner,
-    const base::Closure& request_task,
-    const base::Closure& reply_task) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  const bool posted = blocking_task_runner->PostTaskAndReply(
-      from_here, request_task, reply_task);
-  DCHECK(posted);
-}
-
 // Helper function for binding |path| to GetEntryInfoWithFilePathCallback and
 // create GetEntryInfoCallback.
 void RunGetEntryInfoWithFilePathCallback(
@@ -549,119 +391,6 @@ void RunGetEntryInfoWithFilePathCallback(
 
 }  // namespace
 
-GDataWapiFeedLoader::GDataWapiFeedLoader(
-    GDataDirectoryService* directory_service,
-    DocumentsServiceInterface* documents_service,
-    DriveWebAppsRegistryInterface* webapps_registry,
-    GDataCache* cache,
-    scoped_refptr<base::SequencedTaskRunner> blocking_task_runner)
-    : directory_service_(directory_service),
-      documents_service_(documents_service),
-      webapps_registry_(webapps_registry),
-      cache_(cache),
-      blocking_task_runner_(blocking_task_runner),
-      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
-}
-
-GDataWapiFeedLoader::~GDataWapiFeedLoader() {
-}
-
-void GDataWapiFeedLoader::AddObserver(Observer* observer) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  observers_.AddObserver(observer);
-}
-
-void GDataWapiFeedLoader::RemoveObserver(Observer* observer) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  observers_.RemoveObserver(observer);
-}
-
-// Defines set of parameters sent to callback OnNotifyDocumentFeedFetched().
-// This is a trick to update the number of fetched documents frequently on
-// UI. Due to performance reason, we need to fetch a number of files at
-// a time. However, it'll take long time, and a user has no way to know
-// the current update state. In order to make users confortable,
-// we increment the number of fetched documents with more frequent but smaller
-// steps than actual fetching.
-struct GetDocumentsUiState {
-  explicit GetDocumentsUiState(base::TimeTicks start_time)
-      : num_fetched_documents(0),
-        num_showing_documents(0),
-        start_time(start_time),
-        weak_ptr_factory(this) {
-  }
-
-  // The number of fetched documents.
-  int num_fetched_documents;
-
-  // The number documents shown on UI.
-  int num_showing_documents;
-
-  // When the UI update has started.
-  base::TimeTicks start_time;
-
-  // Time elapsed since the feed fetching was started.
-  base::TimeDelta feed_fetching_elapsed_time;
-
-  base::WeakPtrFactory<GetDocumentsUiState> weak_ptr_factory;
-};
-
-// Defines set of parameters sent to callback OnGetDocuments().
-// TODO(satorux): Move this to a new file: crbug.com/138268
-struct GetDocumentsParams {
-  GetDocumentsParams(int start_changestamp,
-                     int root_feed_changestamp,
-                     std::vector<DocumentFeed*>* feed_list,
-                     bool should_fetch_multiple_feeds,
-                     const FilePath& search_file_path,
-                     const std::string& search_query,
-                     const std::string& directory_resource_id,
-                     const FindEntryCallback& callback,
-                     GetDocumentsUiState* ui_state);
-  ~GetDocumentsParams();
-
-  // Changestamps are positive numbers in increasing order. The difference
-  // between two changestamps is proportional equal to number of items in
-  // delta feed between them - bigger the difference, more likely bigger
-  // number of items in delta feeds.
-  int start_changestamp;
-  int root_feed_changestamp;
-  scoped_ptr<std::vector<DocumentFeed*> > feed_list;
-  // Should we stop after getting first feed chunk, even if there is more
-  // data.
-  bool should_fetch_multiple_feeds;
-  FilePath search_file_path;
-  std::string search_query;
-  std::string directory_resource_id;
-  FindEntryCallback callback;
-  scoped_ptr<GetDocumentsUiState> ui_state;
-};
-
-GetDocumentsParams::GetDocumentsParams(
-    int start_changestamp,
-    int root_feed_changestamp,
-    std::vector<DocumentFeed*>* feed_list,
-    bool should_fetch_multiple_feeds,
-    const FilePath& search_file_path,
-    const std::string& search_query,
-    const std::string& directory_resource_id,
-    const FindEntryCallback& callback,
-    GetDocumentsUiState* ui_state)
-    : start_changestamp(start_changestamp),
-      root_feed_changestamp(root_feed_changestamp),
-      feed_list(feed_list),
-      should_fetch_multiple_feeds(should_fetch_multiple_feeds),
-      search_file_path(search_file_path),
-      search_query(search_query),
-      directory_resource_id(directory_resource_id),
-      callback(callback),
-      ui_state(ui_state) {
-}
-
-GetDocumentsParams::~GetDocumentsParams() {
-  STLDeleteElements(feed_list.get());
-}
-
 // GDataFileSystem::CreateDirectoryParams struct implementation.
 struct GDataFileSystem::CreateDirectoryParams {
   CreateDirectoryParams(const FilePath& created_directory_path,
@@ -975,195 +704,6 @@ void GDataFileSystem::FindEntryByPathSyncOnUIThread(
   directory_service_->FindEntryByPathAndRunSync(search_file_path, callback);
 }
 
-void GDataWapiFeedLoader::ReloadFromServerIfNeeded(
-    ContentOrigin initial_origin,
-    int local_changestamp,
-    const FilePath& search_file_path,
-    const FindEntryCallback& callback) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  DVLOG(1) << "ReloadFeedFromServerIfNeeded local_changestamp="
-           << local_changestamp << ", initial_origin=" << initial_origin;
-
-  // First fetch the latest changestamp to see if there were any new changes
-  // there at all.
-  documents_service_->GetAccountMetadata(
-      base::Bind(&GDataWapiFeedLoader::OnGetAccountMetadata,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 initial_origin,
-                 local_changestamp,
-                 search_file_path,
-                 callback));
-}
-
-void GDataWapiFeedLoader::OnGetAccountMetadata(
-    ContentOrigin initial_origin,
-    int local_changestamp,
-    const FilePath& search_file_path,
-    const FindEntryCallback& callback,
-    GDataErrorCode status,
-    scoped_ptr<base::Value> feed_data) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  GDataFileError error = GDataToGDataFileError(status);
-  if (error != GDATA_FILE_OK) {
-    // Get changes starting from the next changestamp from what we have locally.
-    LoadFromServer(initial_origin,
-                   local_changestamp + 1, 0,
-                   true,  /* should_fetch_multiple_feeds */
-                   search_file_path,
-                   std::string() /* no search query */,
-                   GURL(), /* feed not explicitly set */
-                   std::string() /* no directory resource ID */,
-                   callback,
-                   base::Bind(&GDataWapiFeedLoader::OnFeedFromServerLoaded,
-                              weak_ptr_factory_.GetWeakPtr()));
-    return;
-  }
-
-  scoped_ptr<AccountMetadataFeed> account_metadata;
-  if (feed_data.get()) {
-    account_metadata = AccountMetadataFeed::CreateFrom(*feed_data);
-#ifndef NDEBUG
-    // Save account metadata feed for analysis.
-    const FilePath path =
-        cache_->GetCacheDirectoryPath(GDataCache::CACHE_TYPE_META).Append(
-            kAccountMetadataFile);
-    PostBlockingPoolSequencedTask(
-        FROM_HERE,
-        blocking_task_runner_,
-        base::Bind(&SaveFeedOnBlockingPoolForDebugging,
-                   path, base::Passed(&feed_data)));
-#endif
-  }
-
-  if (!account_metadata.get()) {
-    LoadFromServer(initial_origin,
-                   local_changestamp + 1, 0,
-                   true,  /* should_fetch_multiple_feeds */
-                   search_file_path,
-                   std::string() /* no search query */,
-                   GURL(), /* feed not explicitly set */
-                   std::string() /* no directory resource ID */,
-                   callback,
-                   base::Bind(&GDataWapiFeedLoader::OnFeedFromServerLoaded,
-                              weak_ptr_factory_.GetWeakPtr()));
-    return;
-  }
-
-  webapps_registry_->UpdateFromFeed(account_metadata.get());
-
-  bool changes_detected = true;
-  if (local_changestamp >= account_metadata->largest_changestamp()) {
-    if (local_changestamp > account_metadata->largest_changestamp()) {
-      LOG(WARNING) << "Cached client feed is fresher than server, client = "
-                   << local_changestamp
-                   << ", server = "
-                   << account_metadata->largest_changestamp();
-    }
-    // If our cache holds the latest state from the server, change the
-    // state to FROM_SERVER.
-    directory_service_->set_origin(
-        initial_origin == FROM_CACHE ? FROM_SERVER : initial_origin);
-    changes_detected = false;
-  }
-
-  // No changes detected, continue with search as planned.
-  if (!changes_detected) {
-    if (!callback.is_null()) {
-      directory_service_->FindEntryByPathAndRunSync(search_file_path,
-                                                    callback);
-    }
-    return;
-  }
-
-  // Load changes from the server.
-  LoadFromServer(initial_origin,
-                 local_changestamp > 0 ? local_changestamp + 1 : 0,
-                 account_metadata->largest_changestamp(),
-                 true,  /* should_fetch_multiple_feeds */
-                 search_file_path,
-                 std::string() /* no search query */,
-                 GURL(), /* feed not explicitly set */
-                 std::string() /* no directory resource ID */,
-                 callback,
-                 base::Bind(&GDataWapiFeedLoader::OnFeedFromServerLoaded,
-                            weak_ptr_factory_.GetWeakPtr()));
-}
-
-void GDataWapiFeedLoader::LoadFromServer(
-    ContentOrigin initial_origin,
-    int start_changestamp,
-    int root_feed_changestamp,
-    bool should_fetch_multiple_feeds,
-    const FilePath& search_file_path,
-    const std::string& search_query,
-    const GURL& feed_to_load,
-    const std::string& directory_resource_id,
-    const FindEntryCallback& entry_found_callback,
-    const LoadDocumentFeedCallback& feed_load_callback) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  // |feed_list| will contain the list of all collected feed updates that
-  // we will receive through calls of DocumentsService::GetDocuments().
-  scoped_ptr<std::vector<DocumentFeed*> > feed_list(
-      new std::vector<DocumentFeed*>);
-  const base::TimeTicks start_time = base::TimeTicks::Now();
-  documents_service_->GetDocuments(
-      feed_to_load,
-      start_changestamp,
-      search_query,
-      directory_resource_id,
-      base::Bind(&GDataWapiFeedLoader::OnGetDocuments,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 initial_origin,
-                 feed_load_callback,
-                 base::Owned(new GetDocumentsParams(start_changestamp,
-                                                    root_feed_changestamp,
-                                                    feed_list.release(),
-                                                    should_fetch_multiple_feeds,
-                                                    search_file_path,
-                                                    search_query,
-                                                    directory_resource_id,
-                                                    entry_found_callback,
-                                                    NULL)),
-                 start_time));
-}
-
-void GDataWapiFeedLoader::OnFeedFromServerLoaded(GetDocumentsParams* params,
-                                                 GDataFileError error) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  if (error != GDATA_FILE_OK) {
-    if (!params->callback.is_null())
-      params->callback.Run(error, NULL);
-    return;
-  }
-
-  error = UpdateFromFeed(*params->feed_list,
-                         params->start_changestamp,
-                         params->root_feed_changestamp);
-
-  if (error != GDATA_FILE_OK) {
-    if (!params->callback.is_null())
-      params->callback.Run(error, NULL);
-
-    return;
-  }
-
-  // Save file system metadata to disk.
-  SaveFileSystem();
-
-  // If we had someone to report this too, then this retrieval was done in a
-  // context of search... so continue search.
-  if (!params->callback.is_null()) {
-    directory_service_->FindEntryByPathAndRunSync(params->search_file_path,
-                                                  params->callback);
-  }
-
-  FOR_EACH_OBSERVER(Observer, observers_, OnFeedFromServerLoaded());
-}
-
 void GDataFileSystem::TransferFileFromRemoteToLocal(
     const FilePath& remote_src_file_path,
     const FilePath& local_dest_file_path,
@@ -1222,7 +762,7 @@ void GDataFileSystem::TransferFileFromLocalToRemoteAfterGetEntryInfo(
   }
 
   std::string* resource_id = new std::string;
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&GetDocumentResourceIdOnBlockingPool,
@@ -1271,7 +811,7 @@ void GDataFileSystem::TransferRegularFile(
       new GDataFileError(GDATA_FILE_OK);
   int64* file_size = new int64;
   std::string* content_type = new std::string;
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&GetLocalFileInfoOnBlockingPool,
@@ -1499,7 +1039,7 @@ void GDataFileSystem::OnGetFileCompleteForTransferFile(
   // CopyLocalFileOnBlockingPool.
   GDataFileError* copy_file_error =
       new GDataFileError(GDATA_FILE_OK);
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&CopyLocalFileOnBlockingPool,
@@ -2022,7 +1562,7 @@ void GDataFileSystem::GetResolvedFileByPath(
     FilePath* temp_file_path = new FilePath;
     std::string* mime_type = new std::string;
     GDataFileType* file_type = new GDataFileType(REGULAR_FILE);
-    PostBlockingPoolSequencedTaskAndReply(
+    util::PostBlockingPoolSequencedTaskAndReply(
         FROM_HERE,
         blocking_task_runner_,
         base::Bind(&CreateDocumentJsonFileOnBlockingPool,
@@ -2174,7 +1714,7 @@ void GDataFileSystem::OnGetDocumentEntry(const FilePath& cache_file_path,
                                          scoped_ptr<base::Value> data) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
 
   scoped_ptr<GDataEntry> fresh_entry;
   if (error == GDATA_FILE_OK) {
@@ -2209,7 +1749,7 @@ void GDataFileSystem::OnGetDocumentEntry(const FilePath& cache_file_path,
   directory_service_->RefreshFile(fresh_entry_as_file.Pass());
 
   bool* has_enough_space = new bool(false);
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&GDataCache::FreeDiskSpaceIfNeededFor,
@@ -2542,7 +2082,7 @@ void GDataFileSystem::OnGetFileCompleteForUpdateFile(
   // file size information stored in GDataEntry is not correct.
   GDataFileError* get_size_error = new GDataFileError(GDATA_FILE_ERROR_FAILED);
   int64* file_size = new int64(-1);
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&GetLocalFileSizeOnBlockingPool,
@@ -2655,7 +2195,7 @@ void GDataFileSystem::OnGetAvailableSpace(
     scoped_ptr<base::Value> data) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
   if (error != GDATA_FILE_OK) {
     callback.Run(error, -1, -1);
     return;
@@ -2680,7 +2220,7 @@ void GDataFileSystem::OnCreateDirectoryCompleted(
     scoped_ptr<base::Value> data) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
   if (error != GDATA_FILE_OK) {
     if (!params.callback.is_null())
       params.callback.Run(error);
@@ -2822,191 +2362,6 @@ void GDataFileSystem::SearchAsyncOnUIThread(
       base::Bind(&GDataFileSystem::OnSearch, ui_weak_ptr_, callback));
 }
 
-void GDataWapiFeedLoader::OnGetDocuments(
-    ContentOrigin initial_origin,
-    const LoadDocumentFeedCallback& callback,
-    GetDocumentsParams* params,
-    base::TimeTicks start_time,
-    GDataErrorCode status,
-    scoped_ptr<base::Value> data) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  if (params->feed_list->empty()) {
-    UMA_HISTOGRAM_TIMES("Gdata.InitialFeedLoadTime",
-                        base::TimeTicks::Now() - start_time);
-  }
-
-  GDataFileError error = GDataToGDataFileError(status);
-  if (error == GDATA_FILE_OK &&
-      (!data.get() || data->GetType() != Value::TYPE_DICTIONARY)) {
-    error = GDATA_FILE_ERROR_FAILED;
-  }
-
-  if (error != GDATA_FILE_OK) {
-    directory_service_->set_origin(initial_origin);
-
-    if (!callback.is_null())
-      callback.Run(params, error);
-
-    return;
-  }
-
-  GURL next_feed_url;
-  scoped_ptr<DocumentFeed> current_feed(DocumentFeed::ExtractAndParse(*data));
-  if (!current_feed.get()) {
-    if (!callback.is_null()) {
-      callback.Run(params, GDATA_FILE_ERROR_FAILED);
-    }
-
-    return;
-  }
-  const bool has_next_feed_url = current_feed->GetNextFeedURL(&next_feed_url);
-
-#ifndef NDEBUG
-  // Save initial root feed for analysis.
-  std::string file_name =
-      base::StringPrintf("DEBUG_feed_%d.json",
-                         params->start_changestamp);
-  PostBlockingPoolSequencedTask(
-      FROM_HERE,
-      blocking_task_runner_,
-      base::Bind(&SaveFeedOnBlockingPoolForDebugging,
-                 cache_->GetCacheDirectoryPath(
-                     GDataCache::CACHE_TYPE_META).Append(file_name),
-                 base::Passed(&data)));
-#endif
-
-  // Add the current feed to the list of collected feeds for this directory.
-  params->feed_list->push_back(current_feed.release());
-
-  // Compute and notify the number of entries fetched so far.
-  int num_accumulated_entries = 0;
-  for (size_t i = 0; i < params->feed_list->size(); ++i)
-    num_accumulated_entries += params->feed_list->at(i)->entries().size();
-
-  // Check if we need to collect more data to complete the directory list.
-  if (params->should_fetch_multiple_feeds && has_next_feed_url &&
-      !next_feed_url.is_empty()) {
-    // Post an UI update event to make the UI smoother.
-    GetDocumentsUiState* ui_state = params->ui_state.get();
-    if (ui_state == NULL) {
-      ui_state = new GetDocumentsUiState(base::TimeTicks::Now());
-      params->ui_state.reset(ui_state);
-    }
-    DCHECK(ui_state);
-
-    if ((ui_state->num_fetched_documents - ui_state->num_showing_documents)
-        < kFetchUiUpdateStep) {
-      // Currently the UI update is stopped. Start UI periodic callback.
-      MessageLoop::current()->PostTask(
-          FROM_HERE,
-          base::Bind(&GDataWapiFeedLoader::OnNotifyDocumentFeedFetched,
-                     weak_ptr_factory_.GetWeakPtr(),
-                     ui_state->weak_ptr_factory.GetWeakPtr()));
-    }
-    ui_state->num_fetched_documents = num_accumulated_entries;
-    ui_state->feed_fetching_elapsed_time = base::TimeTicks::Now() - start_time;
-
-    // Kick of the remaining part of the feeds.
-    documents_service_->GetDocuments(
-        next_feed_url,
-        params->start_changestamp,
-        params->search_query,
-        params->directory_resource_id,
-        base::Bind(&GDataWapiFeedLoader::OnGetDocuments,
-                   weak_ptr_factory_.GetWeakPtr(),
-                   initial_origin,
-                   callback,
-                   base::Owned(
-                       new GetDocumentsParams(
-                           params->start_changestamp,
-                           params->root_feed_changestamp,
-                           params->feed_list.release(),
-                           params->should_fetch_multiple_feeds,
-                           params->search_file_path,
-                           params->search_query,
-                           params->directory_resource_id,
-                           params->callback,
-                           params->ui_state.release())),
-                   start_time));
-    return;
-  }
-
-  // Notify the observers that a document feed is fetched.
-  FOR_EACH_OBSERVER(Observer, observers_,
-                    OnDocumentFeedFetched(num_accumulated_entries));
-
-  UMA_HISTOGRAM_TIMES("Gdata.EntireFeedLoadTime",
-                      base::TimeTicks::Now() - start_time);
-
-  if (!callback.is_null())
-    callback.Run(params, error);
-}
-
-void GDataWapiFeedLoader::OnNotifyDocumentFeedFetched(
-    base::WeakPtr<GetDocumentsUiState> ui_state) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  if (!ui_state) {
-    // The ui state instance is already released, which means the fetching
-    // is done and we don't need to update any more.
-    return;
-  }
-
-  base::TimeDelta elapsed_time =
-      base::TimeTicks::Now() - ui_state->start_time;
-
-  if (ui_state->num_showing_documents + kFetchUiUpdateStep <=
-      ui_state->num_fetched_documents) {
-    ui_state->num_showing_documents += kFetchUiUpdateStep;
-    FOR_EACH_OBSERVER(Observer, observers_,
-                      OnDocumentFeedFetched(ui_state->num_showing_documents));
-
-    int num_remaining_ui_updates =
-        (ui_state->num_fetched_documents - ui_state->num_showing_documents)
-        / kFetchUiUpdateStep;
-    if (num_remaining_ui_updates > 0) {
-      // Heuristically, we use fetched time duration to calculate the next
-      // UI update timing.
-      base::TimeDelta remaining_duration =
-          ui_state->feed_fetching_elapsed_time - elapsed_time;
-      MessageLoop::current()->PostDelayedTask(
-          FROM_HERE,
-          base::Bind(&GDataWapiFeedLoader::OnNotifyDocumentFeedFetched,
-                     weak_ptr_factory_.GetWeakPtr(),
-                     ui_state->weak_ptr_factory.GetWeakPtr()),
-          remaining_duration / num_remaining_ui_updates);
-    }
-  }
-}
-
-void GDataWapiFeedLoader::LoadFromCache(
-    bool should_load_from_server,
-    const FilePath& search_file_path,
-    const FindEntryCallback& callback) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  LoadRootFeedParams* params = new LoadRootFeedParams(search_file_path,
-                                                      should_load_from_server,
-                                                      callback);
-  FilePath path = cache_->GetCacheDirectoryPath(GDataCache::CACHE_TYPE_META);
-  if (UseLevelDB()) {
-    path = path.Append(kResourceMetadataDBFile);
-    directory_service_->InitFromDB(path, blocking_task_runner_,
-        base::Bind(
-            &GDataWapiFeedLoader::ContinueWithInitializedDirectoryService,
-            weak_ptr_factory_.GetWeakPtr(),
-            base::Owned(params)));
-  } else {
-    path = path.Append(kFilesystemProtoFile);
-    BrowserThread::GetBlockingPool()->PostTaskAndReply(FROM_HERE,
-        base::Bind(&LoadProtoOnBlockingPool, path, params),
-        base::Bind(&GDataWapiFeedLoader::OnProtoLoaded,
-                   weak_ptr_factory_.GetWeakPtr(),
-                   base::Owned(params)));
-  }
-}
-
 void GDataFileSystem::OnDirectoryChanged(const FilePath& directory_path) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
@@ -3049,99 +2404,6 @@ GDataFileError GDataFileSystem::UpdateFromFeedForTesting(
                                       root_feed_changestamp);
 }
 
-void GDataWapiFeedLoader::OnProtoLoaded(LoadRootFeedParams* params) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  // If we have already received updates from the server, bail out.
-  if (directory_service_->origin() == FROM_SERVER)
-    return;
-
-  // Update directory structure only if everything is OK and we haven't yet
-  // received the feed from the server yet.
-  if (params->load_error == GDATA_FILE_OK) {
-    DVLOG(1) << "ParseFromString";
-    if (directory_service_->ParseFromString(params->proto)) {
-      directory_service_->set_last_serialized(params->last_modified);
-      directory_service_->set_serialized_size(params->proto.size());
-    } else {
-      params->load_error = GDATA_FILE_ERROR_FAILED;
-      LOG(WARNING) << "Parse of cached proto file failed";
-    }
-  }
-
-  ContinueWithInitializedDirectoryService(params, params->load_error);
-}
-
-void GDataWapiFeedLoader::ContinueWithInitializedDirectoryService(
-    LoadRootFeedParams* params,
-    GDataFileError error) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  DVLOG(1) << "Time elapsed to load directory service from disk="
-           << (base::Time::Now() - params->load_start_time).InMilliseconds()
-           << " milliseconds";
-
-  FindEntryCallback callback = params->callback;
-  // If we got feed content from cache, try search over it.
-  if (error == GDATA_FILE_OK && !callback.is_null()) {
-    // Continue file content search operation if the delegate hasn't terminated
-    // this search branch already.
-    directory_service_->FindEntryByPathAndRunSync(params->search_file_path,
-                                                  callback);
-    callback.Reset();
-  }
-
-  if (!params->should_load_from_server)
-    return;
-
-  // Decide the |initial_origin| to pass to ReloadFromServerIfNeeded().
-  // This is used to restore directory content origin to its initial value when
-  // we fail to retrieve the feed from server.
-  // By default, if directory content is not yet initialized, restore content
-  // origin to UNINITIALIZED in case of failure.
-  ContentOrigin initial_origin = UNINITIALIZED;
-  if (directory_service_->origin() != INITIALIZING) {
-    // If directory content is already initialized, restore content origin
-    // to FROM_CACHE in case of failure.
-    initial_origin = FROM_CACHE;
-    directory_service_->set_origin(REFRESHING);
-  }
-
-  // Kick of the retrieval of the feed from server. If we have previously
-  // |reported| to the original callback, then we just need to refresh the
-  // content without continuing search upon operation completion.
-  ReloadFromServerIfNeeded(initial_origin,
-                           directory_service_->largest_changestamp(),
-                           params->search_file_path,
-                           callback);
-}
-
-void GDataWapiFeedLoader::SaveFileSystem() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  if (!ShouldSerializeFileSystemNow(directory_service_->serialized_size(),
-                                    directory_service_->last_serialized())) {
-    return;
-  }
-
-  if (UseLevelDB()) {
-    directory_service_->SaveToDB();
-  } else {
-    const FilePath path =
-        cache_->GetCacheDirectoryPath(GDataCache::CACHE_TYPE_META).Append(
-            kFilesystemProtoFile);
-    scoped_ptr<std::string> serialized_proto(new std::string());
-    directory_service_->SerializeToString(serialized_proto.get());
-    directory_service_->set_last_serialized(base::Time::Now());
-    directory_service_->set_serialized_size(serialized_proto->size());
-    PostBlockingPoolSequencedTask(
-        FROM_HERE,
-        blocking_task_runner_,
-        base::Bind(&SaveProtoOnBlockingPool, path,
-                   base::Passed(serialized_proto.Pass())));
-  }
-}
-
 void GDataFileSystem::OnFilePathUpdated(const FileOperationCallback& callback,
                                         GDataFileError error,
                                         const FilePath& file_path) {
@@ -3159,7 +2421,7 @@ void GDataFileSystem::OnRenameResourceCompleted(
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   FilePath updated_file_path;
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
   if (error == GDATA_FILE_OK)
     error = RenameFileOnFilesystem(file_path, new_name, &updated_file_path);
 
@@ -3174,7 +2436,7 @@ void GDataFileSystem::OnCopyDocumentCompleted(
     scoped_ptr<base::Value> data) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
   if (error != GDATA_FILE_OK) {
     if (!callback.is_null())
       callback.Run(error);
@@ -3214,7 +2476,7 @@ void GDataFileSystem::OnAddEntryToDirectoryCompleted(
     const GURL& document_url) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
   if (error == GDATA_FILE_OK) {
     GDataEntry* entry = directory_service_->FindEntryByPathSync(file_path);
     if (entry) {
@@ -3238,7 +2500,7 @@ void GDataFileSystem::OnRemoveEntryFromDirectoryCompleted(
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   FilePath updated_file_path = file_path;
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
   if (error == GDATA_FILE_OK)
     error = RemoveEntryFromDirectoryOnFilesystem(file_path, dir_path,
                                                  &updated_file_path);
@@ -3254,7 +2516,7 @@ void GDataFileSystem::OnRemovedDocument(
     const GURL& document_url) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
 
   if (error == GDATA_FILE_OK)
     error = RemoveEntryFromFileSystem(file_path);
@@ -3292,7 +2554,7 @@ void GDataFileSystem::OnFileDownloaded(
   // If we don't have enough space, we return PLATFORM_FILE_ERROR_NO_SPACE,
   // and try to free up space, even if the file was downloaded successfully.
   bool* has_enough_space = new bool(false);
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&GDataCache::FreeDiskSpaceIfNeededFor,
@@ -3328,7 +2590,7 @@ void GDataFileSystem::OnFileDownloadedAndSpaceChecked(
     bool* has_enough_space) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  GDataFileError error = GDataToGDataFileError(status);
+  GDataFileError error = util::GDataToGDataFileError(status);
 
   // Make sure that downloaded file is properly stored in cache. We don't have
   // to wait for this operation to finish since the user can already use the
@@ -3345,7 +2607,7 @@ void GDataFileSystem::OnFileDownloadedAndSpaceChecked(
     } else {
       // If we don't have enough space, remove the downloaded file, and
       // report "no space" error.
-      PostBlockingPoolSequencedTask(
+      util::PostBlockingPoolSequencedTask(
           FROM_HERE,
           blocking_task_runner_,
           base::Bind(base::IgnoreResult(&file_util::Delete),
@@ -3466,37 +2728,6 @@ GDataFileError GDataFileSystem::RemoveEntryFromFileSystem(
   return GDATA_FILE_OK;
 }
 
-GDataFileError GDataWapiFeedLoader::UpdateFromFeed(
-    const std::vector<DocumentFeed*>& feed_list,
-    int start_changestamp,
-    int root_feed_changestamp) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DVLOG(1) << "Updating directory with a feed";
-
-  std::set<FilePath> changed_dirs;
-
-  GDataWapiFeedProcessor feed_processor(directory_service_);
-  const GDataFileError error = feed_processor.ApplyFeeds(
-      feed_list,
-      start_changestamp,
-      root_feed_changestamp,
-      &changed_dirs);
-
-  // Don't send directory content change notification while performing
-  // the initial content retrieval.
-  const bool should_notify_directory_changed = (start_changestamp != 0);
-  if (should_notify_directory_changed) {
-    for (std::set<FilePath>::iterator dir_iter = changed_dirs.begin();
-        dir_iter != changed_dirs.end(); ++dir_iter) {
-      FOR_EACH_OBSERVER(Observer, observers_,
-                        OnDirectoryChanged(*dir_iter));
-    }
-  }
-
-  return error;
-}
-
-
 // static
 void GDataFileSystem::RemoveStaleEntryOnUpload(const std::string& resource_id,
                                                GDataDirectory* parent_dir,
@@ -3984,7 +3215,7 @@ void GDataFileSystem::OnGetCacheFilePathCompleteForCloseFile(
   // the cache file.
   base::PlatformFileInfo* file_info = new base::PlatformFileInfo;
   bool* get_file_info_result = new bool(false);
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&GetFileInfoOnBlockingPool,
@@ -4165,7 +3396,7 @@ void GDataFileSystem::CheckLocalModificationAndRunAfterGetCacheFile(
   // If the cache is dirty, obtain the file info from the cache file itself.
   base::PlatformFileInfo* file_info = new base::PlatformFileInfo;
   bool* get_file_info_result = new bool(false);
-  PostBlockingPoolSequencedTaskAndReply(
+  util::PostBlockingPoolSequencedTaskAndReply(
       FROM_HERE,
       blocking_task_runner_,
       base::Bind(&GetFileInfoOnBlockingPool,
diff --git a/chrome/browser/chromeos/gdata/gdata_file_system.h b/chrome/browser/chromeos/gdata/gdata_file_system.h
index 707ddc3..bc3d247 100644
--- a/chrome/browser/chromeos/gdata/gdata_file_system.h
+++ b/chrome/browser/chromeos/gdata/gdata_file_system.h
@@ -19,6 +19,7 @@
 #include "chrome/browser/chromeos/gdata/gdata_file_system_interface.h"
 #include "chrome/browser/chromeos/gdata/gdata_errorcode.h"
 #include "chrome/browser/chromeos/gdata/gdata_files.h"
+#include "chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.h"
 #include "chrome/browser/chromeos/gdata/gdata_wapi_feed_processor.h"
 #include "chrome/browser/prefs/pref_change_registrar.h"
 #include "content/public/browser/notification_observer.h"
@@ -34,167 +35,8 @@ namespace gdata {
 class DocumentsServiceInterface;
 class DriveWebAppsRegistryInterface;
 class GDataWapiFeedLoader;
-struct GetDocumentsParams;
-struct GetDocumentsUiState;
 struct UploadFileInfo;
 
-// Callback run as a response to LoadFromServer.
-//
-// TODO(satorux): Move this to a new file: crbug.com/138268
-typedef base::Callback<void(GetDocumentsParams* params,
-                            GDataFileError error)>
-    LoadDocumentFeedCallback;
-
-// GDataWapiFeedLoader is used to load feeds from WAPI (codename for
-// Documents List API) and load the cached proto file.
-//
-// TODO(satorux): Move this to a new file: crbug.com/138268
-class GDataWapiFeedLoader {
- public:
-  // Used to notify events from the loader.
-  // All events are notified on UI thread.
-  class Observer {
-   public:
-    // Triggered when a content of a directory has been changed.
-    // |directory_path| is a virtual directory path representing the
-    // changed directory.
-    virtual void OnDirectoryChanged(const FilePath& directory_path) {}
-
-    // Triggered when a document feed is fetched. |num_accumulated_entries|
-    // tells the number of entries fetched so far.
-    virtual void OnDocumentFeedFetched(int num_accumulated_entries) {}
-
-    // Triggered when the feed from the server is loaded.
-    virtual void OnFeedFromServerLoaded() {}
-
-   protected:
-    virtual ~Observer() {}
-  };
-
-  GDataWapiFeedLoader(
-      GDataDirectoryService* directory_service,
-      DocumentsServiceInterface* documents_service,
-      DriveWebAppsRegistryInterface* webapps_registry,
-      GDataCache* cache,
-      scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_);
-  ~GDataWapiFeedLoader();
-
-  // Adds and removes the observer.
-  void AddObserver(Observer* observer);
-  void RemoveObserver(Observer* observer);
-
-  // Starts root feed load from the cache. If successful, it will try to find
-  // the file upon retrieval completion. In addition to that, it will
-  // initiate retrieval of the root feed from the server unless
-  // |should_load_from_server| is set to false. |should_load_from_server| is
-  // false only for testing.
-  void LoadFromCache(bool should_load_from_server,
-                     const FilePath& search_file_path,
-                     const FindEntryCallback& callback);
-
-  // Starts root feed load from the server. Value of |start_changestamp|
-  // determines the type of feed to load - 0 means root feed, every other
-  // value would trigger delta feed.
-  // In the case of loading the root feed we use |root_feed_changestamp| as its
-  // initial changestamp value since it does not come with that info.
-  // When done |load_feed_callback| is invoked.
-  // |entry_found_callback| is used only when this is invoked while searching
-  // for file info, and is used in |load_feed_callback|. If successful, it will
-  // try to find the file upon retrieval completion.
-  // |should_fetch_multiple_feeds| is true iff don't want to stop feed loading
-  // after we retrieve first feed chunk.
-  // If invoked as a part of content search, query will be set in
-  // |search_query|.
-  // If |feed_to_load| is set, this is feed url that will be used to load feed.
-  void LoadFromServer(
-      ContentOrigin initial_origin,
-      int start_changestamp,
-      int root_feed_changestamp,
-      bool should_fetch_multiple_feeds,
-      const FilePath& search_file_path,
-      const std::string& search_query,
-      const GURL& feed_to_load,
-      const std::string& directory_resource_id,
-      const FindEntryCallback& entry_found_callback,
-      const LoadDocumentFeedCallback& feed_load_callback);
-
-  // Retrieves account metadata and determines from the last change timestamp
-  // if the feed content loading from the server needs to be initiated.
-  void ReloadFromServerIfNeeded(
-      ContentOrigin initial_origin,
-      int local_changestamp,
-      const FilePath& search_file_path,
-      const FindEntryCallback& callback);
-
-  // Updates whole directory structure feeds collected in |feed_list|.
-  // On success, returns PLATFORM_FILE_OK. Record file statistics as UMA
-  // histograms.
-  //
-  // See comments at GDataWapiFeedProcessor::ApplyFeeds() for
-  // |start_changestamp| and |root_feed_changestamp|.
-  GDataFileError UpdateFromFeed(
-    const std::vector<DocumentFeed*>& feed_list,
-    int start_changestamp,
-    int root_feed_changestamp);
-
- private:
-  // Callback for handling root directory refresh from the cache.
-  void OnProtoLoaded(LoadRootFeedParams* params);
-
-  // Continues handling root directory refresh after the directory service
-  // is fully loaded.
-  void ContinueWithInitializedDirectoryService(LoadRootFeedParams* params,
-                                               GDataFileError error);
-
-  // Helper callback for handling results of metadata retrieval initiated from
-  // ReloadFeedFromServerIfNeeded(). This method makes a decision about fetching
-  // the content of the root feed during the root directory refresh process.
-  void OnGetAccountMetadata(
-      ContentOrigin initial_origin,
-      int local_changestamp,
-      const FilePath& search_file_path,
-      const FindEntryCallback& callback,
-      GDataErrorCode status,
-      scoped_ptr<base::Value> feed_data);
-
-  // Callback for handling feed content fetching while searching for file info.
-  // This callback is invoked after async feed fetch operation that was
-  // invoked by StartDirectoryRefresh() completes. This callback will update
-  // the content of the refreshed directory object and continue initially
-  // started FindEntryByPath() request.
-  void OnFeedFromServerLoaded(GetDocumentsParams* params,
-                              GDataFileError error);
-
-  // Callback for handling response from |GDataDocumentsService::GetDocuments|.
-  // Invokes |callback| when done.
-  void OnGetDocuments(
-      ContentOrigin initial_origin,
-      const LoadDocumentFeedCallback& callback,
-      GetDocumentsParams* params,
-      base::TimeTicks start_time,
-      GDataErrorCode status,
-      scoped_ptr<base::Value> data);
-
-  // Save filesystem to disk.
-  void SaveFileSystem();
-
-  // Callback for handling UI updates caused by document fetching.
-  void OnNotifyDocumentFeedFetched(
-      base::WeakPtr<GetDocumentsUiState> ui_state);
-
-  GDataDirectoryService* directory_service_;  // Not owned.
-  DocumentsServiceInterface* documents_service_;  // Not owned.
-  DriveWebAppsRegistryInterface* webapps_registry_;  // Not owned.
-  GDataCache* cache_;  // Not owned.
-  scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
-  ObserverList<Observer> observers_;
-
-  // Note: This should remain the last member so it'll be destroyed and
-  // invalidate its weak pointers before any other members are destroyed.
-  base::WeakPtrFactory<GDataWapiFeedLoader> weak_ptr_factory_;
-  DISALLOW_COPY_AND_ASSIGN(GDataWapiFeedLoader);
-};
-
 // The production implementation of GDataFileSystemInterface.
 class GDataFileSystem : public GDataFileSystemInterface,
                         public GDataWapiFeedLoader::Observer,
diff --git a/chrome/browser/chromeos/gdata/gdata_util.cc b/chrome/browser/chromeos/gdata/gdata_util.cc
index 3db1670..92a3c78 100644
--- a/chrome/browser/chromeos/gdata/gdata_util.cc
+++ b/chrome/browser/chromeos/gdata/gdata_util.cc
@@ -21,6 +21,7 @@
 #include "base/stringprintf.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "base/time.h"
+#include "base/tracked_objects.h"
 #include "chrome/browser/chromeos/gdata/file_write_helper.h"
 #include "chrome/browser/chromeos/gdata/gdata.pb.h"
 #include "chrome/browser/chromeos/gdata/gdata_file_system_interface.h"
@@ -604,5 +605,47 @@ void PrepareWritableFileAndRun(Profile* profile,
   }
 }
 
+GDataFileError GDataToGDataFileError(GDataErrorCode status) {
+  switch (status) {
+    case HTTP_SUCCESS:
+    case HTTP_CREATED:
+      return GDATA_FILE_OK;
+    case HTTP_UNAUTHORIZED:
+    case HTTP_FORBIDDEN:
+      return GDATA_FILE_ERROR_ACCESS_DENIED;
+    case HTTP_NOT_FOUND:
+      return GDATA_FILE_ERROR_NOT_FOUND;
+    case GDATA_PARSE_ERROR:
+    case GDATA_FILE_ERROR:
+      return GDATA_FILE_ERROR_ABORT;
+    case GDATA_NO_CONNECTION:
+      return GDATA_FILE_ERROR_NO_CONNECTION;
+    default:
+      return GDATA_FILE_ERROR_FAILED;
+  }
+}
+
+void PostBlockingPoolSequencedTask(
+    const tracked_objects::Location& from_here,
+    base::SequencedTaskRunner* blocking_task_runner,
+    const base::Closure& task) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  const bool posted = blocking_task_runner->PostTask(from_here, task);
+  DCHECK(posted);
+}
+
+void PostBlockingPoolSequencedTaskAndReply(
+    const tracked_objects::Location& from_here,
+    base::SequencedTaskRunner* blocking_task_runner,
+    const base::Closure& request_task,
+    const base::Closure& reply_task) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  const bool posted = blocking_task_runner->PostTaskAndReply(
+      from_here, request_task, reply_task);
+  DCHECK(posted);
+}
+
 }  // namespace util
 }  // namespace gdata
diff --git a/chrome/browser/chromeos/gdata/gdata_util.h b/chrome/browser/chromeos/gdata/gdata_util.h
index 04e5e6d..d7640db 100644
--- a/chrome/browser/chromeos/gdata/gdata_util.h
+++ b/chrome/browser/chromeos/gdata/gdata_util.h
@@ -18,6 +18,14 @@
 class FilePath;
 class Profile;
 
+namespace base {
+class SequencedTaskRunner;
+}  // namespace base
+
+namespace tracked_objects {
+class Location;
+}  // tracked_objects
+
 namespace gdata {
 namespace util {
 
@@ -112,7 +120,7 @@ std::string FormatTimeAsString(const base::Time& time);
 
 // Callback type for PrepareWritableFilePathAndRun.
 typedef base::Callback<void (GDataFileError, const FilePath& path)>
-   OpenFileCallback;
+    OpenFileCallback;
 
 // Invokes |callback| on blocking thread pool, after converting virtual |path|
 // string like "/special/drive/foo.txt" to the concrete local cache file path.
@@ -126,6 +134,24 @@ void PrepareWritableFileAndRun(Profile* profile,
                                const FilePath& path,
                                const OpenFileCallback& callback);
 
+// Converts gdata error code into file platform error code.
+GDataFileError GDataToGDataFileError(GDataErrorCode status);
+
+// Wrapper around BrowserThread::PostTask to post a task to the blocking
+// pool with the given sequence token.
+void PostBlockingPoolSequencedTask(
+    const tracked_objects::Location& from_here,
+    base::SequencedTaskRunner* blocking_task_runner,
+    const base::Closure& task);
+
+// Similar to PostBlockingPoolSequencedTask() but this one takes a reply
+// callback that runs on the calling thread.
+void PostBlockingPoolSequencedTaskAndReply(
+    const tracked_objects::Location& from_here,
+    base::SequencedTaskRunner* blocking_task_runner,
+    const base::Closure& request_task,
+    const base::Closure& reply_task);
+
 }  // namespace util
 }  // namespace gdata
 
diff --git a/chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.cc b/chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.cc
new file mode 100644
index 0000000..b5eb7cd
--- /dev/null
+++ b/chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.cc
@@ -0,0 +1,717 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.h"
+
+#include "base/command_line.h"
+#include "base/file_util.h"
+#include "base/json/json_reader.h"
+#include "base/json/json_writer.h"
+#include "base/message_loop.h"
+#include "base/metrics/histogram.h"
+#include "base/stringprintf.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "chrome/browser/chromeos/gdata/drive_webapps_registry.h"
+#include "chrome/browser/chromeos/gdata/gdata_cache.h"
+#include "chrome/browser/chromeos/gdata/gdata_documents_service.h"
+#include "chrome/browser/chromeos/gdata/gdata_util.h"
+#include "chrome/browser/chromeos/gdata/gdata_wapi_feed_processor.h"
+#include "chrome/common/chrome_switches.h"
+#include "content/public/browser/browser_thread.h"
+
+using content::BrowserThread;
+
+namespace gdata {
+
+namespace {
+
+const FilePath::CharType kAccountMetadataFile[] =
+    FILE_PATH_LITERAL("account_metadata.json");
+const FilePath::CharType kFilesystemProtoFile[] =
+    FILE_PATH_LITERAL("file_system.pb");
+const FilePath::CharType kResourceMetadataDBFile[] =
+    FILE_PATH_LITERAL("resource_metadata.db");
+
+// Update the fetch progress UI per every this number of feeds.
+const int kFetchUiUpdateStep = 10;
+
+// Schedule for dumping root file system proto buffers to disk depending its
+// total protobuffer size in MB.
+typedef struct {
+  double size;
+  int timeout;
+} SerializationTimetable;
+
+SerializationTimetable kSerializeTimetable[] = {
+#ifndef NDEBUG
+    {0.5, 0},    // Less than 0.5MB, dump immediately.
+    {-1,  1},    // Any size, dump if older than 1 minute.
+#else
+    {0.5, 0},    // Less than 0.5MB, dump immediately.
+    {1.0, 15},   // Less than 1.0MB, dump after 15 minutes.
+    {2.0, 30},
+    {4.0, 60},
+    {-1,  120},  // Any size, dump if older than 120 minutes.
+#endif
+};
+
+// Loads the file at |path| into the string |serialized_proto| on a blocking
+// thread.
+void LoadProtoOnBlockingPool(const FilePath& path,
+                             LoadRootFeedParams* params) {
+  base::PlatformFileInfo info;
+  if (!file_util::GetFileInfo(path, &info)) {
+    params->load_error = GDATA_FILE_ERROR_NOT_FOUND;
+    return;
+  }
+  params->last_modified = info.last_modified;
+  if (!file_util::ReadFileToString(path, &params->proto)) {
+    LOG(WARNING) << "Proto file not found at " << path.value();
+    params->load_error = GDATA_FILE_ERROR_NOT_FOUND;
+    return;
+  }
+  params->load_error = GDATA_FILE_OK;
+}
+
+// Saves json file content content in |feed| to |file_pathname| on blocking
+// pool. Used for debugging.
+void SaveFeedOnBlockingPoolForDebugging(
+    const FilePath& file_path,
+    scoped_ptr<base::Value> feed) {
+  std::string json;
+  base::JSONWriter::WriteWithOptions(feed.get(),
+                                     base::JSONWriter::OPTIONS_PRETTY_PRINT,
+                                     &json);
+
+  int file_size = static_cast<int>(json.length());
+  if (file_util::WriteFile(file_path, json.data(), file_size) != file_size) {
+    LOG(WARNING) << "GData metadata file can't be stored at "
+                 << file_path.value();
+    if (!file_util::Delete(file_path, true)) {
+      LOG(WARNING) << "GData metadata file can't be deleted at "
+                   << file_path.value();
+      return;
+    }
+  }
+}
+
+// Returns true if file system is due to be serialized on disk based on it
+// |serialized_size| and |last_serialized| timestamp.
+bool ShouldSerializeFileSystemNow(size_t serialized_size,
+                                  const base::Time& last_serialized) {
+  const double size_in_mb = serialized_size / 1048576.0;
+  const int last_proto_dump_in_min =
+      (base::Time::Now() - last_serialized).InMinutes();
+  for (size_t i = 0; i < arraysize(kSerializeTimetable); i++) {
+    if ((size_in_mb < kSerializeTimetable[i].size ||
+         kSerializeTimetable[i].size == -1) &&
+        last_proto_dump_in_min >= kSerializeTimetable[i].timeout) {
+      return true;
+    }
+  }
+  return false;
+}
+
+// Saves the string |serialized_proto| to a file at |path| on a blocking thread.
+void SaveProtoOnBlockingPool(const FilePath& path,
+                             scoped_ptr<std::string> serialized_proto) {
+  const int file_size = static_cast<int>(serialized_proto->length());
+  if (file_util::WriteFile(path, serialized_proto->data(), file_size) !=
+      file_size) {
+    LOG(WARNING) << "GData proto file can't be stored at "
+                 << path.value();
+    if (!file_util::Delete(path, true)) {
+      LOG(WARNING) << "GData proto file can't be deleted at "
+                   << path.value();
+    }
+  }
+}
+
+bool UseLevelDB() {
+  return CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kUseLevelDBForGData);
+}
+
+}  // namespace
+
+GetDocumentsParams::GetDocumentsParams(
+    int start_changestamp,
+    int root_feed_changestamp,
+    std::vector<DocumentFeed*>* feed_list,
+    bool should_fetch_multiple_feeds,
+    const FilePath& search_file_path,
+    const std::string& search_query,
+    const std::string& directory_resource_id,
+    const FindEntryCallback& callback,
+    GetDocumentsUiState* ui_state)
+    : start_changestamp(start_changestamp),
+      root_feed_changestamp(root_feed_changestamp),
+      feed_list(feed_list),
+      should_fetch_multiple_feeds(should_fetch_multiple_feeds),
+      search_file_path(search_file_path),
+      search_query(search_query),
+      directory_resource_id(directory_resource_id),
+      callback(callback),
+      ui_state(ui_state) {
+}
+
+GetDocumentsParams::~GetDocumentsParams() {
+  STLDeleteElements(feed_list.get());
+}
+
+// Defines set of parameters sent to callback OnNotifyDocumentFeedFetched().
+// This is a trick to update the number of fetched documents frequently on
+// UI. Due to performance reason, we need to fetch a number of files at
+// a time. However, it'll take long time, and a user has no way to know
+// the current update state. In order to make users confortable,
+// we increment the number of fetched documents with more frequent but smaller
+// steps than actual fetching.
+struct GetDocumentsUiState {
+  explicit GetDocumentsUiState(base::TimeTicks start_time)
+      : num_fetched_documents(0),
+        num_showing_documents(0),
+        start_time(start_time),
+        weak_ptr_factory(this) {
+  }
+
+  // The number of fetched documents.
+  int num_fetched_documents;
+
+  // The number documents shown on UI.
+  int num_showing_documents;
+
+  // When the UI update has started.
+  base::TimeTicks start_time;
+
+  // Time elapsed since the feed fetching was started.
+  base::TimeDelta feed_fetching_elapsed_time;
+
+  base::WeakPtrFactory<GetDocumentsUiState> weak_ptr_factory;
+};
+
+GDataWapiFeedLoader::GDataWapiFeedLoader(
+    GDataDirectoryService* directory_service,
+    DocumentsServiceInterface* documents_service,
+    DriveWebAppsRegistryInterface* webapps_registry,
+    GDataCache* cache,
+    scoped_refptr<base::SequencedTaskRunner> blocking_task_runner)
+    : directory_service_(directory_service),
+      documents_service_(documents_service),
+      webapps_registry_(webapps_registry),
+      cache_(cache),
+      blocking_task_runner_(blocking_task_runner),
+      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+}
+
+GDataWapiFeedLoader::~GDataWapiFeedLoader() {
+}
+
+void GDataWapiFeedLoader::AddObserver(Observer* observer) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  observers_.AddObserver(observer);
+}
+
+void GDataWapiFeedLoader::RemoveObserver(Observer* observer) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  observers_.RemoveObserver(observer);
+}
+
+void GDataWapiFeedLoader::ReloadFromServerIfNeeded(
+    ContentOrigin initial_origin,
+    int local_changestamp,
+    const FilePath& search_file_path,
+    const FindEntryCallback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  DVLOG(1) << "ReloadFeedFromServerIfNeeded local_changestamp="
+           << local_changestamp << ", initial_origin=" << initial_origin;
+
+  // First fetch the latest changestamp to see if there were any new changes
+  // there at all.
+  documents_service_->GetAccountMetadata(
+      base::Bind(&GDataWapiFeedLoader::OnGetAccountMetadata,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 initial_origin,
+                 local_changestamp,
+                 search_file_path,
+                 callback));
+}
+
+void GDataWapiFeedLoader::OnGetAccountMetadata(
+    ContentOrigin initial_origin,
+    int local_changestamp,
+    const FilePath& search_file_path,
+    const FindEntryCallback& callback,
+    GDataErrorCode status,
+    scoped_ptr<base::Value> feed_data) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  GDataFileError error = util::GDataToGDataFileError(status);
+  if (error != GDATA_FILE_OK) {
+    // Get changes starting from the next changestamp from what we have locally.
+    LoadFromServer(initial_origin,
+                   local_changestamp + 1, 0,
+                   true,  /* should_fetch_multiple_feeds */
+                   search_file_path,
+                   std::string() /* no search query */,
+                   GURL(), /* feed not explicitly set */
+                   std::string() /* no directory resource ID */,
+                   callback,
+                   base::Bind(&GDataWapiFeedLoader::OnFeedFromServerLoaded,
+                              weak_ptr_factory_.GetWeakPtr()));
+    return;
+  }
+
+  scoped_ptr<AccountMetadataFeed> account_metadata;
+  if (feed_data.get()) {
+    account_metadata = AccountMetadataFeed::CreateFrom(*feed_data);
+#ifndef NDEBUG
+    // Save account metadata feed for analysis.
+    const FilePath path =
+        cache_->GetCacheDirectoryPath(GDataCache::CACHE_TYPE_META).Append(
+            kAccountMetadataFile);
+    util::PostBlockingPoolSequencedTask(
+        FROM_HERE,
+        blocking_task_runner_,
+        base::Bind(&SaveFeedOnBlockingPoolForDebugging,
+                   path, base::Passed(&feed_data)));
+#endif
+  }
+
+  if (!account_metadata.get()) {
+    LoadFromServer(initial_origin,
+                   local_changestamp + 1, 0,
+                   true,  /* should_fetch_multiple_feeds */
+                   search_file_path,
+                   std::string() /* no search query */,
+                   GURL(), /* feed not explicitly set */
+                   std::string() /* no directory resource ID */,
+                   callback,
+                   base::Bind(&GDataWapiFeedLoader::OnFeedFromServerLoaded,
+                              weak_ptr_factory_.GetWeakPtr()));
+    return;
+  }
+
+  webapps_registry_->UpdateFromFeed(account_metadata.get());
+
+  bool changes_detected = true;
+  if (local_changestamp >= account_metadata->largest_changestamp()) {
+    if (local_changestamp > account_metadata->largest_changestamp()) {
+      LOG(WARNING) << "Cached client feed is fresher than server, client = "
+                   << local_changestamp
+                   << ", server = "
+                   << account_metadata->largest_changestamp();
+    }
+    // If our cache holds the latest state from the server, change the
+    // state to FROM_SERVER.
+    directory_service_->set_origin(
+        initial_origin == FROM_CACHE ? FROM_SERVER : initial_origin);
+    changes_detected = false;
+  }
+
+  // No changes detected, continue with search as planned.
+  if (!changes_detected) {
+    if (!callback.is_null()) {
+      directory_service_->FindEntryByPathAndRunSync(search_file_path,
+                                                    callback);
+    }
+    return;
+  }
+
+  // Load changes from the server.
+  LoadFromServer(initial_origin,
+                 local_changestamp > 0 ? local_changestamp + 1 : 0,
+                 account_metadata->largest_changestamp(),
+                 true,  /* should_fetch_multiple_feeds */
+                 search_file_path,
+                 std::string() /* no search query */,
+                 GURL(), /* feed not explicitly set */
+                 std::string() /* no directory resource ID */,
+                 callback,
+                 base::Bind(&GDataWapiFeedLoader::OnFeedFromServerLoaded,
+                            weak_ptr_factory_.GetWeakPtr()));
+}
+
+void GDataWapiFeedLoader::LoadFromServer(
+    ContentOrigin initial_origin,
+    int start_changestamp,
+    int root_feed_changestamp,
+    bool should_fetch_multiple_feeds,
+    const FilePath& search_file_path,
+    const std::string& search_query,
+    const GURL& feed_to_load,
+    const std::string& directory_resource_id,
+    const FindEntryCallback& entry_found_callback,
+    const LoadDocumentFeedCallback& feed_load_callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  // |feed_list| will contain the list of all collected feed updates that
+  // we will receive through calls of DocumentsService::GetDocuments().
+  scoped_ptr<std::vector<DocumentFeed*> > feed_list(
+      new std::vector<DocumentFeed*>);
+  const base::TimeTicks start_time = base::TimeTicks::Now();
+  documents_service_->GetDocuments(
+      feed_to_load,
+      start_changestamp,
+      search_query,
+      directory_resource_id,
+      base::Bind(&GDataWapiFeedLoader::OnGetDocuments,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 initial_origin,
+                 feed_load_callback,
+                 base::Owned(new GetDocumentsParams(start_changestamp,
+                                                    root_feed_changestamp,
+                                                    feed_list.release(),
+                                                    should_fetch_multiple_feeds,
+                                                    search_file_path,
+                                                    search_query,
+                                                    directory_resource_id,
+                                                    entry_found_callback,
+                                                    NULL)),
+                 start_time));
+}
+
+void GDataWapiFeedLoader::OnFeedFromServerLoaded(GetDocumentsParams* params,
+                                                 GDataFileError error) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  if (error != GDATA_FILE_OK) {
+    if (!params->callback.is_null())
+      params->callback.Run(error, NULL);
+    return;
+  }
+
+  error = UpdateFromFeed(*params->feed_list,
+                         params->start_changestamp,
+                         params->root_feed_changestamp);
+
+  if (error != GDATA_FILE_OK) {
+    if (!params->callback.is_null())
+      params->callback.Run(error, NULL);
+
+    return;
+  }
+
+  // Save file system metadata to disk.
+  SaveFileSystem();
+
+  // If we had someone to report this too, then this retrieval was done in a
+  // context of search... so continue search.
+  if (!params->callback.is_null()) {
+    directory_service_->FindEntryByPathAndRunSync(params->search_file_path,
+                                                  params->callback);
+  }
+
+  FOR_EACH_OBSERVER(Observer, observers_, OnFeedFromServerLoaded());
+}
+
+void GDataWapiFeedLoader::OnGetDocuments(
+    ContentOrigin initial_origin,
+    const LoadDocumentFeedCallback& callback,
+    GetDocumentsParams* params,
+    base::TimeTicks start_time,
+    GDataErrorCode status,
+    scoped_ptr<base::Value> data) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  if (params->feed_list->empty()) {
+    UMA_HISTOGRAM_TIMES("Gdata.InitialFeedLoadTime",
+                        base::TimeTicks::Now() - start_time);
+  }
+
+  GDataFileError error = util::GDataToGDataFileError(status);
+  if (error == GDATA_FILE_OK &&
+      (!data.get() || data->GetType() != Value::TYPE_DICTIONARY)) {
+    error = GDATA_FILE_ERROR_FAILED;
+  }
+
+  if (error != GDATA_FILE_OK) {
+    directory_service_->set_origin(initial_origin);
+
+    if (!callback.is_null())
+      callback.Run(params, error);
+
+    return;
+  }
+
+  GURL next_feed_url;
+  scoped_ptr<DocumentFeed> current_feed(DocumentFeed::ExtractAndParse(*data));
+  if (!current_feed.get()) {
+    if (!callback.is_null()) {
+      callback.Run(params, GDATA_FILE_ERROR_FAILED);
+    }
+
+    return;
+  }
+  const bool has_next_feed_url = current_feed->GetNextFeedURL(&next_feed_url);
+
+#ifndef NDEBUG
+  // Save initial root feed for analysis.
+  std::string file_name =
+      base::StringPrintf("DEBUG_feed_%d.json",
+                         params->start_changestamp);
+  util::PostBlockingPoolSequencedTask(
+      FROM_HERE,
+      blocking_task_runner_,
+      base::Bind(&SaveFeedOnBlockingPoolForDebugging,
+                 cache_->GetCacheDirectoryPath(
+                     GDataCache::CACHE_TYPE_META).Append(file_name),
+                 base::Passed(&data)));
+#endif
+
+  // Add the current feed to the list of collected feeds for this directory.
+  params->feed_list->push_back(current_feed.release());
+
+  // Compute and notify the number of entries fetched so far.
+  int num_accumulated_entries = 0;
+  for (size_t i = 0; i < params->feed_list->size(); ++i)
+    num_accumulated_entries += params->feed_list->at(i)->entries().size();
+
+  // Check if we need to collect more data to complete the directory list.
+  if (params->should_fetch_multiple_feeds && has_next_feed_url &&
+      !next_feed_url.is_empty()) {
+    // Post an UI update event to make the UI smoother.
+    GetDocumentsUiState* ui_state = params->ui_state.get();
+    if (ui_state == NULL) {
+      ui_state = new GetDocumentsUiState(base::TimeTicks::Now());
+      params->ui_state.reset(ui_state);
+    }
+    DCHECK(ui_state);
+
+    if ((ui_state->num_fetched_documents - ui_state->num_showing_documents)
+        < kFetchUiUpdateStep) {
+      // Currently the UI update is stopped. Start UI periodic callback.
+      MessageLoop::current()->PostTask(
+          FROM_HERE,
+          base::Bind(&GDataWapiFeedLoader::OnNotifyDocumentFeedFetched,
+                     weak_ptr_factory_.GetWeakPtr(),
+                     ui_state->weak_ptr_factory.GetWeakPtr()));
+    }
+    ui_state->num_fetched_documents = num_accumulated_entries;
+    ui_state->feed_fetching_elapsed_time = base::TimeTicks::Now() - start_time;
+
+    // Kick of the remaining part of the feeds.
+    documents_service_->GetDocuments(
+        next_feed_url,
+        params->start_changestamp,
+        params->search_query,
+        params->directory_resource_id,
+        base::Bind(&GDataWapiFeedLoader::OnGetDocuments,
+                   weak_ptr_factory_.GetWeakPtr(),
+                   initial_origin,
+                   callback,
+                   base::Owned(
+                       new GetDocumentsParams(
+                           params->start_changestamp,
+                           params->root_feed_changestamp,
+                           params->feed_list.release(),
+                           params->should_fetch_multiple_feeds,
+                           params->search_file_path,
+                           params->search_query,
+                           params->directory_resource_id,
+                           params->callback,
+                           params->ui_state.release())),
+                   start_time));
+    return;
+  }
+
+  // Notify the observers that a document feed is fetched.
+  FOR_EACH_OBSERVER(Observer, observers_,
+                    OnDocumentFeedFetched(num_accumulated_entries));
+
+  UMA_HISTOGRAM_TIMES("Gdata.EntireFeedLoadTime",
+                      base::TimeTicks::Now() - start_time);
+
+  if (!callback.is_null())
+    callback.Run(params, error);
+}
+
+void GDataWapiFeedLoader::OnNotifyDocumentFeedFetched(
+    base::WeakPtr<GetDocumentsUiState> ui_state) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  if (!ui_state) {
+    // The ui state instance is already released, which means the fetching
+    // is done and we don't need to update any more.
+    return;
+  }
+
+  base::TimeDelta elapsed_time =
+      base::TimeTicks::Now() - ui_state->start_time;
+
+  if (ui_state->num_showing_documents + kFetchUiUpdateStep <=
+      ui_state->num_fetched_documents) {
+    ui_state->num_showing_documents += kFetchUiUpdateStep;
+    FOR_EACH_OBSERVER(Observer, observers_,
+                      OnDocumentFeedFetched(ui_state->num_showing_documents));
+
+    int num_remaining_ui_updates =
+        (ui_state->num_fetched_documents - ui_state->num_showing_documents)
+        / kFetchUiUpdateStep;
+    if (num_remaining_ui_updates > 0) {
+      // Heuristically, we use fetched time duration to calculate the next
+      // UI update timing.
+      base::TimeDelta remaining_duration =
+          ui_state->feed_fetching_elapsed_time - elapsed_time;
+      MessageLoop::current()->PostDelayedTask(
+          FROM_HERE,
+          base::Bind(&GDataWapiFeedLoader::OnNotifyDocumentFeedFetched,
+                     weak_ptr_factory_.GetWeakPtr(),
+                     ui_state->weak_ptr_factory.GetWeakPtr()),
+          remaining_duration / num_remaining_ui_updates);
+    }
+  }
+}
+
+void GDataWapiFeedLoader::LoadFromCache(
+    bool should_load_from_server,
+    const FilePath& search_file_path,
+    const FindEntryCallback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  LoadRootFeedParams* params = new LoadRootFeedParams(search_file_path,
+                                                      should_load_from_server,
+                                                      callback);
+  FilePath path = cache_->GetCacheDirectoryPath(GDataCache::CACHE_TYPE_META);
+  if (UseLevelDB()) {
+    path = path.Append(kResourceMetadataDBFile);
+    directory_service_->InitFromDB(path, blocking_task_runner_,
+        base::Bind(
+            &GDataWapiFeedLoader::ContinueWithInitializedDirectoryService,
+            weak_ptr_factory_.GetWeakPtr(),
+            base::Owned(params)));
+  } else {
+    path = path.Append(kFilesystemProtoFile);
+    BrowserThread::GetBlockingPool()->PostTaskAndReply(FROM_HERE,
+        base::Bind(&LoadProtoOnBlockingPool, path, params),
+        base::Bind(&GDataWapiFeedLoader::OnProtoLoaded,
+                   weak_ptr_factory_.GetWeakPtr(),
+                   base::Owned(params)));
+  }
+}
+
+void GDataWapiFeedLoader::OnProtoLoaded(LoadRootFeedParams* params) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  // If we have already received updates from the server, bail out.
+  if (directory_service_->origin() == FROM_SERVER)
+    return;
+
+  // Update directory structure only if everything is OK and we haven't yet
+  // received the feed from the server yet.
+  if (params->load_error == GDATA_FILE_OK) {
+    DVLOG(1) << "ParseFromString";
+    if (directory_service_->ParseFromString(params->proto)) {
+      directory_service_->set_last_serialized(params->last_modified);
+      directory_service_->set_serialized_size(params->proto.size());
+    } else {
+      params->load_error = GDATA_FILE_ERROR_FAILED;
+      LOG(WARNING) << "Parse of cached proto file failed";
+    }
+  }
+
+  ContinueWithInitializedDirectoryService(params, params->load_error);
+}
+
+void GDataWapiFeedLoader::ContinueWithInitializedDirectoryService(
+    LoadRootFeedParams* params,
+    GDataFileError error) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  DVLOG(1) << "Time elapsed to load directory service from disk="
+           << (base::Time::Now() - params->load_start_time).InMilliseconds()
+           << " milliseconds";
+
+  FindEntryCallback callback = params->callback;
+  // If we got feed content from cache, try search over it.
+  if (error == GDATA_FILE_OK && !callback.is_null()) {
+    // Continue file content search operation if the delegate hasn't terminated
+    // this search branch already.
+    directory_service_->FindEntryByPathAndRunSync(params->search_file_path,
+                                                  callback);
+    callback.Reset();
+  }
+
+  if (!params->should_load_from_server)
+    return;
+
+  // Decide the |initial_origin| to pass to ReloadFromServerIfNeeded().
+  // This is used to restore directory content origin to its initial value when
+  // we fail to retrieve the feed from server.
+  // By default, if directory content is not yet initialized, restore content
+  // origin to UNINITIALIZED in case of failure.
+  ContentOrigin initial_origin = UNINITIALIZED;
+  if (directory_service_->origin() != INITIALIZING) {
+    // If directory content is already initialized, restore content origin
+    // to FROM_CACHE in case of failure.
+    initial_origin = FROM_CACHE;
+    directory_service_->set_origin(REFRESHING);
+  }
+
+  // Kick of the retrieval of the feed from server. If we have previously
+  // |reported| to the original callback, then we just need to refresh the
+  // content without continuing search upon operation completion.
+  ReloadFromServerIfNeeded(initial_origin,
+                           directory_service_->largest_changestamp(),
+                           params->search_file_path,
+                           callback);
+}
+
+void GDataWapiFeedLoader::SaveFileSystem() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  if (!ShouldSerializeFileSystemNow(directory_service_->serialized_size(),
+                                    directory_service_->last_serialized())) {
+    return;
+  }
+
+  if (UseLevelDB()) {
+    directory_service_->SaveToDB();
+  } else {
+    const FilePath path =
+        cache_->GetCacheDirectoryPath(GDataCache::CACHE_TYPE_META).Append(
+            kFilesystemProtoFile);
+    scoped_ptr<std::string> serialized_proto(new std::string());
+    directory_service_->SerializeToString(serialized_proto.get());
+    directory_service_->set_last_serialized(base::Time::Now());
+    directory_service_->set_serialized_size(serialized_proto->size());
+    util::PostBlockingPoolSequencedTask(
+        FROM_HERE,
+        blocking_task_runner_,
+        base::Bind(&SaveProtoOnBlockingPool, path,
+                   base::Passed(serialized_proto.Pass())));
+  }
+}
+
+GDataFileError GDataWapiFeedLoader::UpdateFromFeed(
+    const std::vector<DocumentFeed*>& feed_list,
+    int start_changestamp,
+    int root_feed_changestamp) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DVLOG(1) << "Updating directory with a feed";
+
+  std::set<FilePath> changed_dirs;
+
+  GDataWapiFeedProcessor feed_processor(directory_service_);
+  const GDataFileError error = feed_processor.ApplyFeeds(
+      feed_list,
+      start_changestamp,
+      root_feed_changestamp,
+      &changed_dirs);
+
+  // Don't send directory content change notification while performing
+  // the initial content retrieval.
+  const bool should_notify_directory_changed = (start_changestamp != 0);
+  if (should_notify_directory_changed) {
+    for (std::set<FilePath>::iterator dir_iter = changed_dirs.begin();
+        dir_iter != changed_dirs.end(); ++dir_iter) {
+      FOR_EACH_OBSERVER(Observer, observers_,
+                        OnDirectoryChanged(*dir_iter));
+    }
+  }
+
+  return error;
+}
+
+}  // namespace gdata
diff --git a/chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.h b/chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.h
new file mode 100644
index 0000000..f1f3d05
--- /dev/null
+++ b/chrome/browser/chromeos/gdata/gdata_wapi_feed_loader.h
@@ -0,0 +1,206 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_CHROMEOS_GDATA_GDATA_WAPI_FEED_LOADER_H_
+#define CHROME_BROWSER_CHROMEOS_GDATA_GDATA_WAPI_FEED_LOADER_H_
+
+#include "base/callback.h"
+#include "base/file_path.h"
+#include "base/observer_list.h"
+#include "chrome/browser/chromeos/gdata/gdata_errorcode.h"
+#include "chrome/browser/chromeos/gdata/gdata_files.h"
+
+namespace gdata {
+
+class DriveWebAppsRegistryInterface;
+class DocumentsServiceInterface;
+class GDataCache;
+struct GetDocumentsUiState;
+
+// Set of parameters sent to LoadDocumentFeedCallback callback.
+struct GetDocumentsParams {
+  GetDocumentsParams(int start_changestamp,
+                     int root_feed_changestamp,
+                     std::vector<DocumentFeed*>* feed_list,
+                     bool should_fetch_multiple_feeds,
+                     const FilePath& search_file_path,
+                     const std::string& search_query,
+                     const std::string& directory_resource_id,
+                     const FindEntryCallback& callback,
+                     GetDocumentsUiState* ui_state);
+  ~GetDocumentsParams();
+
+  // Changestamps are positive numbers in increasing order. The difference
+  // between two changestamps is proportional equal to number of items in
+  // delta feed between them - bigger the difference, more likely bigger
+  // number of items in delta feeds.
+  int start_changestamp;
+  int root_feed_changestamp;
+  scoped_ptr<std::vector<DocumentFeed*> > feed_list;
+  // Should we stop after getting first feed chunk, even if there is more
+  // data.
+  bool should_fetch_multiple_feeds;
+  FilePath search_file_path;
+  std::string search_query;
+  std::string directory_resource_id;
+  FindEntryCallback callback;
+  scoped_ptr<GetDocumentsUiState> ui_state;
+};
+
+// Callback run as a response to LoadFromServer.
+typedef base::Callback<void(GetDocumentsParams* params,
+                            GDataFileError error)>
+    LoadDocumentFeedCallback;
+
+// GDataWapiFeedLoader is used to load feeds from WAPI (codename for
+// Documents List API) and load the cached proto file.
+class GDataWapiFeedLoader {
+ public:
+  // Used to notify events from the loader.
+  // All events are notified on UI thread.
+  class Observer {
+   public:
+    // Triggered when a content of a directory has been changed.
+    // |directory_path| is a virtual directory path representing the
+    // changed directory.
+    virtual void OnDirectoryChanged(const FilePath& directory_path) {}
+
+    // Triggered when a document feed is fetched. |num_accumulated_entries|
+    // tells the number of entries fetched so far.
+    virtual void OnDocumentFeedFetched(int num_accumulated_entries) {}
+
+    // Triggered when the feed from the server is loaded.
+    virtual void OnFeedFromServerLoaded() {}
+
+   protected:
+    virtual ~Observer() {}
+  };
+
+  GDataWapiFeedLoader(
+      GDataDirectoryService* directory_service,
+      DocumentsServiceInterface* documents_service,
+      DriveWebAppsRegistryInterface* webapps_registry,
+      GDataCache* cache,
+      scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_);
+  ~GDataWapiFeedLoader();
+
+  // Adds and removes the observer.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  // Starts root feed load from the cache. If successful, it will try to find
+  // the file upon retrieval completion. In addition to that, it will
+  // initiate retrieval of the root feed from the server unless
+  // |should_load_from_server| is set to false. |should_load_from_server| is
+  // false only for testing.
+  void LoadFromCache(bool should_load_from_server,
+                     const FilePath& search_file_path,
+                     const FindEntryCallback& callback);
+
+  // Starts root feed load from the server. Value of |start_changestamp|
+  // determines the type of feed to load - 0 means root feed, every other
+  // value would trigger delta feed.
+  // In the case of loading the root feed we use |root_feed_changestamp| as its
+  // initial changestamp value since it does not come with that info.
+  // When done |load_feed_callback| is invoked.
+  // |entry_found_callback| is used only when this is invoked while searching
+  // for file info, and is used in |load_feed_callback|. If successful, it will
+  // try to find the file upon retrieval completion.
+  // |should_fetch_multiple_feeds| is true iff don't want to stop feed loading
+  // after we retrieve first feed chunk.
+  // If invoked as a part of content search, query will be set in
+  // |search_query|.
+  // If |feed_to_load| is set, this is feed url that will be used to load feed.
+  void LoadFromServer(
+      ContentOrigin initial_origin,
+      int start_changestamp,
+      int root_feed_changestamp,
+      bool should_fetch_multiple_feeds,
+      const FilePath& search_file_path,
+      const std::string& search_query,
+      const GURL& feed_to_load,
+      const std::string& directory_resource_id,
+      const FindEntryCallback& entry_found_callback,
+      const LoadDocumentFeedCallback& feed_load_callback);
+
+  // Retrieves account metadata and determines from the last change timestamp
+  // if the feed content loading from the server needs to be initiated.
+  void ReloadFromServerIfNeeded(
+      ContentOrigin initial_origin,
+      int local_changestamp,
+      const FilePath& search_file_path,
+      const FindEntryCallback& callback);
+
+  // Updates whole directory structure feeds collected in |feed_list|.
+  // On success, returns PLATFORM_FILE_OK. Record file statistics as UMA
+  // histograms.
+  //
+  // See comments at GDataWapiFeedProcessor::ApplyFeeds() for
+  // |start_changestamp| and |root_feed_changestamp|.
+  GDataFileError UpdateFromFeed(
+    const std::vector<DocumentFeed*>& feed_list,
+    int start_changestamp,
+    int root_feed_changestamp);
+
+ private:
+  // Callback for handling root directory refresh from the cache.
+  void OnProtoLoaded(LoadRootFeedParams* params);
+
+  // Continues handling root directory refresh after the directory service
+  // is fully loaded.
+  void ContinueWithInitializedDirectoryService(LoadRootFeedParams* params,
+                                               GDataFileError error);
+
+  // Helper callback for handling results of metadata retrieval initiated from
+  // ReloadFeedFromServerIfNeeded(). This method makes a decision about fetching
+  // the content of the root feed during the root directory refresh process.
+  void OnGetAccountMetadata(
+      ContentOrigin initial_origin,
+      int local_changestamp,
+      const FilePath& search_file_path,
+      const FindEntryCallback& callback,
+      GDataErrorCode status,
+      scoped_ptr<base::Value> feed_data);
+
+  // Callback for handling feed content fetching while searching for file info.
+  // This callback is invoked after async feed fetch operation that was
+  // invoked by StartDirectoryRefresh() completes. This callback will update
+  // the content of the refreshed directory object and continue initially
+  // started FindEntryByPath() request.
+  void OnFeedFromServerLoaded(GetDocumentsParams* params,
+                              GDataFileError error);
+
+  // Callback for handling response from |GDataDocumentsService::GetDocuments|.
+  // Invokes |callback| when done.
+  void OnGetDocuments(
+      ContentOrigin initial_origin,
+      const LoadDocumentFeedCallback& callback,
+      GetDocumentsParams* params,
+      base::TimeTicks start_time,
+      GDataErrorCode status,
+      scoped_ptr<base::Value> data);
+
+  // Save filesystem to disk.
+  void SaveFileSystem();
+
+  // Callback for handling UI updates caused by document fetching.
+  void OnNotifyDocumentFeedFetched(
+      base::WeakPtr<GetDocumentsUiState> ui_state);
+
+  GDataDirectoryService* directory_service_;  // Not owned.
+  DocumentsServiceInterface* documents_service_;  // Not owned.
+  DriveWebAppsRegistryInterface* webapps_registry_;  // Not owned.
+  GDataCache* cache_;  // Not owned.
+  scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
+  ObserverList<Observer> observers_;
+
+  // Note: This should remain the last member so it'll be destroyed and
+  // invalidate its weak pointers before any other members are destroyed.
+  base::WeakPtrFactory<GDataWapiFeedLoader> weak_ptr_factory_;
+  DISALLOW_COPY_AND_ASSIGN(GDataWapiFeedLoader);
+};
+
+}  // namespace gdata
+
+#endif  // CHROME_BROWSER_CHROMEOS_GDATA_GDATA_WAPI_FEED_LOADER_H_
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index 64753f1..6322452 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -593,6 +593,8 @@
         'browser/chromeos/gdata/gdata_uploader.h',
         'browser/chromeos/gdata/gdata_util.cc',
         'browser/chromeos/gdata/gdata_util.h',
+        'browser/chromeos/gdata/gdata_wapi_feed_loader.cc',
+        'browser/chromeos/gdata/gdata_wapi_feed_loader.h',
         'browser/chromeos/gdata/gdata_wapi_feed_processor.cc',
         'browser/chromeos/gdata/gdata_wapi_feed_processor.h',
         'browser/chromeos/gdata/gdata_wapi_parser.cc',