Add FileSystemID parameter to IsolatedContext::RegisterFileSystemForPath.

With this change, nested filesystems mounted onto isolated context
can remember its original filesystem id, that unblocks the issue 370782
of drag-and-drop support in chromeos::FileSystemBackend.

BUG=370782, 386062
TBR=kaznacheev, benwells, dmichael, sky

Review URL: https://codereview.chromium.org/341043008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278666 0039d316-1c4b-4281-b951-d872f2087c98

18 files changed, 94 insertions, 41 deletions

diff --git a/chrome/browser/chromeos/drive/file_system_util_unittest.cc b/chrome/browser/chromeos/drive/file_system_util_unittest.cc
index 157dfff..d60e738 100644
--- a/chrome/browser/chromeos/drive/file_system_util_unittest.cc
+++ b/chrome/browser/chromeos/drive/file_system_util_unittest.cc
@@ -199,6 +199,7 @@ TEST(FileSystemUtilTest, ExtractDrivePathFromFileSystemUrl) {
   std::string isolated_id =
       fileapi::IsolatedContext::GetInstance()->RegisterFileSystemForPath(
           fileapi::kFileSystemTypeNativeForPlatformApp,
+          std::string(),
           GetDriveMountPointPath(&profile).AppendASCII("bar/buz"),
           &isolated_name);
   EXPECT_EQ(
diff --git a/chrome/browser/chromeos/fileapi/file_system_backend.cc b/chrome/browser/chromeos/fileapi/file_system_backend.cc
index 04fd83f..ff18a44 100644
--- a/chrome/browser/chromeos/fileapi/file_system_backend.cc
+++ b/chrome/browser/chromeos/fileapi/file_system_backend.cc
@@ -96,12 +96,13 @@ void FileSystemBackend::ResolveURL(const fileapi::FileSystemURL& url,
                                    const OpenFileSystemCallback& callback) {
   std::string id;
   fileapi::FileSystemType type;
+  std::string cracked_id;
   base::FilePath path;
   fileapi::FileSystemMountOption option;
   if (!mount_points_->CrackVirtualPath(
-           url.virtual_path(), &id, &type, &path, &option) &&
+           url.virtual_path(), &id, &type, &cracked_id, &path, &option) &&
       !system_mount_points_->CrackVirtualPath(
-           url.virtual_path(), &id, &type, &path, &option)) {
+           url.virtual_path(), &id, &type, &cracked_id, &path, &option)) {
     // Not under a mount point, so return an error, since the root is not
     // accessible.
     GURL root_url = GURL(fileapi::GetExternalFileSystemRootURIString(
@@ -188,12 +189,13 @@ void FileSystemBackend::GrantFileAccessToExtension(
 
   std::string id;
   fileapi::FileSystemType type;
+  std::string cracked_id;
   base::FilePath path;
   fileapi::FileSystemMountOption option;
-  if (!mount_points_->CrackVirtualPath(virtual_path,
-                                       &id, &type, &path, &option) &&
-      !system_mount_points_->CrackVirtualPath(virtual_path,
-                                              &id, &type, &path, &option)) {
+  if (!mount_points_->CrackVirtualPath(virtual_path, &id, &type, &cracked_id,
+                                       &path, &option) &&
+      !system_mount_points_->CrackVirtualPath(virtual_path, &id, &type,
+                                              &cracked_id, &path, &option)) {
     return;
   }
 
@@ -278,7 +280,8 @@ fileapi::FileSystemOperation* FileSystemBackend::CreateFileSystemOperation(
 bool FileSystemBackend::SupportsStreaming(
     const fileapi::FileSystemURL& url) const {
   return url.type() == fileapi::kFileSystemTypeDrive ||
-         url.type() == fileapi::kFileSystemTypeProvided;
+         url.type() == fileapi::kFileSystemTypeProvided ||
+         url.type() == fileapi::kFileSystemTypeDeviceMediaAsFileStorage;
 }
 
 scoped_ptr<webkit_blob::FileStreamReader>
diff --git a/chrome/browser/devtools/devtools_file_helper.cc b/chrome/browser/devtools/devtools_file_helper.cc
index 03ab906..d1fee7b 100644
--- a/chrome/browser/devtools/devtools_file_helper.cc
+++ b/chrome/browser/devtools/devtools_file_helper.cc
@@ -145,7 +145,8 @@ std::string RegisterFileSystem(WebContents* web_contents,
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   CHECK(web_contents->GetURL().SchemeIs(content::kChromeDevToolsScheme));
   std::string file_system_id = isolated_context()->RegisterFileSystemForPath(
-      fileapi::kFileSystemTypeNativeLocal, path, registered_name);
+      fileapi::kFileSystemTypeNativeLocal, std::string(), path,
+      registered_name);
 
   content::ChildProcessSecurityPolicy* policy =
       content::ChildProcessSecurityPolicy::GetInstance();
diff --git a/chrome/browser/extensions/api/file_handlers/app_file_handler_util.cc b/chrome/browser/extensions/api/file_handlers/app_file_handler_util.cc
index 277bc99..91b24c5 100644
--- a/chrome/browser/extensions/api/file_handlers/app_file_handler_util.cc
+++ b/chrome/browser/extensions/api/file_handlers/app_file_handler_util.cc
@@ -299,7 +299,7 @@ GrantedFileEntry CreateFileEntry(
   DCHECK(isolated_context);
 
   result.filesystem_id = isolated_context->RegisterFileSystemForPath(
-      fileapi::kFileSystemTypeNativeForPlatformApp, path,
+      fileapi::kFileSystemTypeNativeForPlatformApp, std::string(), path,
       &result.registered_name);
 
   content::ChildProcessSecurityPolicy* policy =
@@ -368,8 +368,10 @@ bool ValidateFileEntryAndGetPath(
       .Append(relative_path);
   fileapi::FileSystemType type;
   fileapi::FileSystemMountOption mount_option;
+  std::string cracked_id;
   if (!context->CrackVirtualPath(
-          virtual_path, &filesystem_id, &type, file_path, &mount_option)) {
+          virtual_path, &filesystem_id, &type, &cracked_id, file_path,
+          &mount_option)) {
     *error = kInvalidParameters;
     return false;
   }
diff --git a/chrome/browser/media_galleries/fileapi/media_file_validator_browsertest.cc b/chrome/browser/media_galleries/fileapi/media_file_validator_browsertest.cc
index c2e3082..530701f 100644
--- a/chrome/browser/media_galleries/fileapi/media_file_validator_browsertest.cc
+++ b/chrome/browser/media_galleries/fileapi/media_file_validator_browsertest.cc
@@ -129,7 +129,8 @@ class MediaFileValidatorTest : public InProcessBrowserTest {
     ASSERT_TRUE(base::CreateDirectory(dest_path));
     std::string dest_fsid =
         fileapi::IsolatedContext::GetInstance()->RegisterFileSystemForPath(
-            fileapi::kFileSystemTypeNativeMedia, dest_path, NULL);
+            fileapi::kFileSystemTypeNativeMedia, std::string(), dest_path,
+            NULL);
 
     size_t extension_index = filename.find_last_of(".");
     ASSERT_NE(std::string::npos, extension_index);
diff --git a/chrome/browser/media_galleries/fileapi/native_media_file_util_unittest.cc b/chrome/browser/media_galleries/fileapi/native_media_file_util_unittest.cc
index 7a96738..1e2579d 100644
--- a/chrome/browser/media_galleries/fileapi/native_media_file_util_unittest.cc
+++ b/chrome/browser/media_galleries/fileapi/native_media_file_util_unittest.cc
@@ -138,7 +138,7 @@ class NativeMediaFileUtilTest : public testing::Test {
         content::CreateAllowFileAccessOptions());
 
     filesystem_id_ = isolated_context()->RegisterFileSystemForPath(
-        fileapi::kFileSystemTypeNativeMedia, root_path(), NULL);
+        fileapi::kFileSystemTypeNativeMedia, std::string(), root_path(), NULL);
 
     isolated_context()->AddReference(filesystem_id_);
   }
diff --git a/chrome/browser/renderer_host/pepper/pepper_isolated_file_system_message_filter.cc b/chrome/browser/renderer_host/pepper/pepper_isolated_file_system_message_filter.cc
index f587af1..7852132 100644
--- a/chrome/browser/renderer_host/pepper/pepper_isolated_file_system_message_filter.cc
+++ b/chrome/browser/renderer_host/pepper/pepper_isolated_file_system_message_filter.cc
@@ -117,6 +117,7 @@ std::string PepperIsolatedFileSystemMessageFilter::CreateCrxFileSystem(
   std::string kFirstLevelDirectory("crxfs");
   return fileapi::IsolatedContext::GetInstance()->RegisterFileSystemForPath(
       fileapi::kFileSystemTypeNativeLocal,
+      std::string(),
       extension->path(),
       &kFirstLevelDirectory);
 }
diff --git a/content/browser/fileapi/external_mount_points_unittest.cc b/content/browser/fileapi/external_mount_points_unittest.cc
index a1b0787..fa0d1f5 100644
--- a/content/browser/fileapi/external_mount_points_unittest.cc
+++ b/content/browser/fileapi/external_mount_points_unittest.cc
@@ -456,11 +456,13 @@ TEST(ExternalMountPointsTest, CrackVirtualPath) {
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(kTestCases); ++i) {
     std::string cracked_name;
     fileapi::FileSystemType cracked_type;
+    std::string cracked_id;
     base::FilePath cracked_path;
     fileapi::FileSystemMountOption cracked_option;
     EXPECT_EQ(kTestCases[i].expect_valid,
               mount_points->CrackVirtualPath(base::FilePath(kTestCases[i].path),
-                  &cracked_name, &cracked_type, &cracked_path, &cracked_option))
+                  &cracked_name, &cracked_type, &cracked_id, &cracked_path,
+                  &cracked_option))
         << "Test case index: " << i;
 
     if (!kTestCases[i].expect_valid)
@@ -473,6 +475,9 @@ TEST(ExternalMountPointsTest, CrackVirtualPath) {
         << "Test case index: " << i;
     EXPECT_EQ(kTestCases[i].expect_name, cracked_name)
         << "Test case index: " << i;
+    // As of now we don't mount other filesystems with non-empty filesystem_id
+    // onto external mount points.
+    EXPECT_TRUE(cracked_id.empty()) << "Test case index: " << i;
   }
 }
 
@@ -493,13 +498,16 @@ TEST(ExternalMountPointsTest, MountOption) {
 
   std::string name;
   fileapi::FileSystemType type;
+  std::string cracked_id;
   fileapi::FileSystemMountOption option;
   base::FilePath path;
   EXPECT_TRUE(mount_points->CrackVirtualPath(
-      base::FilePath(FPL("nosync/file")), &name, &type, &path, &option));
+      base::FilePath(FPL("nosync/file")), &name, &type, &cracked_id, &path,
+      &option));
   EXPECT_EQ(fileapi::COPY_SYNC_OPTION_NO_SYNC, option.copy_sync_option());
   EXPECT_TRUE(mount_points->CrackVirtualPath(
-      base::FilePath(FPL("sync/file")), &name, &type, &path, &option));
+      base::FilePath(FPL("sync/file")), &name, &type, &cracked_id, &path,
+      &option));
   EXPECT_EQ(fileapi::COPY_SYNC_OPTION_SYNC, option.copy_sync_option());
 }
 
diff --git a/content/browser/fileapi/file_system_context_unittest.cc b/content/browser/fileapi/file_system_context_unittest.cc
index 099e30c..e746a6a 100644
--- a/content/browser/fileapi/file_system_context_unittest.cc
+++ b/content/browser/fileapi/file_system_context_unittest.cc
@@ -114,6 +114,7 @@ TEST_F(FileSystemContextTest, NullExternalMountPoints) {
   std::string isolated_id =
       IsolatedContext::GetInstance()->RegisterFileSystemForPath(
           fileapi::kFileSystemTypeNativeLocal,
+          std::string(),
           base::FilePath(DRIVE FPL("/test/isolated/root")),
           &isolated_name);
   // Register system external mount point.
@@ -203,6 +204,7 @@ TEST_F(FileSystemContextTest, CrackFileSystemURL) {
   const std::string kIsolatedFileSystemID =
       IsolatedContext::GetInstance()->RegisterFileSystemForPath(
           fileapi::kFileSystemTypeNativeLocal,
+          std::string(),
           base::FilePath(DRIVE FPL("/test/isolated/root")),
           &isolated_file_system_name);
   // Register system external mount point.
@@ -357,6 +359,7 @@ TEST_F(FileSystemContextTest, CanServeURLRequest) {
   std::string isolated_fs_id =
       IsolatedContext::GetInstance()->RegisterFileSystemForPath(
           fileapi::kFileSystemTypeNativeLocal,
+          std::string(),
           base::FilePath(DRIVE FPL("/test/isolated/root")),
           &isolated_fs_name);
   cracked_url = context->CrackURL(
diff --git a/content/browser/fileapi/isolated_context_unittest.cc b/content/browser/fileapi/isolated_context_unittest.cc
index be754d4..be5cc8e 100644
--- a/content/browser/fileapi/isolated_context_unittest.cc
+++ b/content/browser/fileapi/isolated_context_unittest.cc
@@ -102,15 +102,17 @@ TEST_F(IsolatedContextTest, RegisterAndRevokeTest) {
         .AppendASCII(names_[i]);
     std::string cracked_id;
     base::FilePath cracked_path;
+    std::string cracked_inner_id;
     fileapi::FileSystemType cracked_type;
     FileSystemMountOption cracked_option;
     ASSERT_TRUE(isolated_context()->CrackVirtualPath(
-        virtual_path, &cracked_id, &cracked_type, &cracked_path,
-        &cracked_option));
+        virtual_path, &cracked_id, &cracked_type, &cracked_inner_id,
+        &cracked_path, &cracked_option));
     ASSERT_EQ(kTestPaths[i].NormalizePathSeparators().value(),
               cracked_path.value());
     ASSERT_EQ(id_, cracked_id);
     ASSERT_EQ(kFileSystemTypeDragged, cracked_type);
+    EXPECT_TRUE(cracked_inner_id.empty());
   }
 
   // Make sure GetRegisteredPath returns false for id_ since it is
@@ -122,7 +124,8 @@ TEST_F(IsolatedContextTest, RegisterAndRevokeTest) {
   isolated_context()->RemoveReference(id_);
 
   std::string id2 = isolated_context()->RegisterFileSystemForPath(
-      kFileSystemTypeNativeLocal, base::FilePath(DRIVE FPL("/foo")), NULL);
+      kFileSystemTypeNativeLocal, std::string(),
+      base::FilePath(DRIVE FPL("/foo")), NULL);
 
   // Make sure the GetDraggedFileInfo returns false for both ones.
   ASSERT_FALSE(isolated_context()->GetDraggedFileInfo(id2, &toplevels));
@@ -134,11 +137,11 @@ TEST_F(IsolatedContextTest, RegisterAndRevokeTest) {
 
   // Try registering three more file systems for the same path as id2.
   std::string id3 = isolated_context()->RegisterFileSystemForPath(
-      kFileSystemTypeNativeLocal, path, NULL);
+      kFileSystemTypeNativeLocal, std::string(), path, NULL);
   std::string id4 = isolated_context()->RegisterFileSystemForPath(
-      kFileSystemTypeNativeLocal, path, NULL);
+      kFileSystemTypeNativeLocal, std::string(), path, NULL);
   std::string id5 = isolated_context()->RegisterFileSystemForPath(
-      kFileSystemTypeNativeLocal, path, NULL);
+      kFileSystemTypeNativeLocal, std::string(), path, NULL);
 
   // Remove file system for id4.
   isolated_context()->AddReference(id4);
@@ -201,21 +204,23 @@ TEST_F(IsolatedContextTest, CrackWithRelativePaths) {
       std::string cracked_id;
       base::FilePath cracked_path;
       fileapi::FileSystemType cracked_type;
+      std::string cracked_inner_id;
       FileSystemMountOption cracked_option;
       if (!relatives[j].valid) {
         ASSERT_FALSE(isolated_context()->CrackVirtualPath(
-            virtual_path, &cracked_id, &cracked_type, &cracked_path,
-            &cracked_option));
+            virtual_path, &cracked_id, &cracked_type, &cracked_inner_id,
+            &cracked_path, &cracked_option));
         continue;
       }
       ASSERT_TRUE(isolated_context()->CrackVirtualPath(
-          virtual_path, &cracked_id, &cracked_type, &cracked_path,
-          &cracked_option));
+          virtual_path, &cracked_id, &cracked_type, &cracked_inner_id,
+          &cracked_path, &cracked_option));
       ASSERT_EQ(kTestPaths[i].Append(relatives[j].path)
                     .NormalizePathSeparators().value(),
                 cracked_path.value());
       ASSERT_EQ(id_, cracked_id);
       ASSERT_EQ(kFileSystemTypeDragged, cracked_type);
+      EXPECT_TRUE(cracked_inner_id.empty());
     }
   }
 }
@@ -276,7 +281,7 @@ TEST_F(IsolatedContextTest, TestWithVirtualRoot) {
   // that has no corresponding platform directory.
   base::FilePath virtual_path = isolated_context()->CreateVirtualRootPath(id_);
   ASSERT_TRUE(isolated_context()->CrackVirtualPath(
-      virtual_path, &cracked_id, NULL, &cracked_path, &cracked_option));
+      virtual_path, &cracked_id, NULL, NULL, &cracked_path, &cracked_option));
   ASSERT_EQ(FPL(""), cracked_path.value());
   ASSERT_EQ(id_, cracked_id);
 
@@ -285,7 +290,7 @@ TEST_F(IsolatedContextTest, TestWithVirtualRoot) {
   virtual_path = isolated_context()->CreateVirtualRootPath(
       id_).AppendASCII("foo");
   ASSERT_FALSE(isolated_context()->CrackVirtualPath(
-      virtual_path, &cracked_id, NULL, &cracked_path, &cracked_option));
+      virtual_path, &cracked_id, NULL, NULL, &cracked_path, &cracked_option));
 }
 
 TEST_F(IsolatedContextTest, CanHandleURL) {
@@ -342,11 +347,14 @@ TEST_F(IsolatedContextTest, VirtualFileSystemTests) {
 
   std::string cracked_id;
   base::FilePath cracked_path;
+  std::string cracked_inner_id;
   FileSystemMountOption cracked_option;
   ASSERT_TRUE(isolated_context()->CrackVirtualPath(
-      whole_virtual_path, &cracked_id, NULL, &cracked_path, &cracked_option));
+      whole_virtual_path, &cracked_id, NULL, &cracked_inner_id,
+      &cracked_path, &cracked_option));
   ASSERT_EQ(database_fsid, cracked_id);
   ASSERT_EQ(test_virtual_path, cracked_path);
+  EXPECT_TRUE(cracked_inner_id.empty());
 }
 
 }  // namespace content
diff --git a/content/browser/fileapi/transient_file_util_unittest.cc b/content/browser/fileapi/transient_file_util_unittest.cc
index 876733ab..96df84f 100644
--- a/content/browser/fileapi/transient_file_util_unittest.cc
+++ b/content/browser/fileapi/transient_file_util_unittest.cc
@@ -47,6 +47,7 @@ class TransientFileUtilTest : public testing::Test {
     std::string name = "tmp";
     std::string fsid = isolated_context->RegisterFileSystemForPath(
         fileapi::kFileSystemTypeForTransientFile,
+        std::string(),
         *file_path,
         &name);
     ASSERT_TRUE(!fsid.empty());
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index 164f613..e14b364 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -764,7 +764,8 @@ void RenderViewHostImpl::DragTargetDragEnter(
 
     std::string register_name;
     std::string filesystem_id = isolated_context->RegisterFileSystemForPath(
-        file_system_url.type(), file_system_url.path(), &register_name);
+        file_system_url.type(), file_system_url.filesystem_id(),
+        file_system_url.path(), &register_name);
     policy->GrantReadFileSystem(renderer_id, filesystem_id);
 
     // Note: We are using the origin URL provided by the sender here. It may be
diff --git a/extensions/browser/api/runtime/runtime_api.cc b/extensions/browser/api/runtime/runtime_api.cc
index 733ea1f..e2e522f 100644
--- a/extensions/browser/api/runtime/runtime_api.cc
+++ b/extensions/browser/api/runtime/runtime_api.cc
@@ -528,7 +528,7 @@ RuntimeGetPackageDirectoryEntryFunction::Run() {
   std::string relative_path = kPackageDirectoryPath;
   base::FilePath path = extension_->path();
   std::string filesystem_id = isolated_context->RegisterFileSystemForPath(
-      fileapi::kFileSystemTypeNativeLocal, path, &relative_path);
+      fileapi::kFileSystemTypeNativeLocal, std::string(), path, &relative_path);
 
   int renderer_id = render_view_host_->GetProcess()->GetID();
   content::ChildProcessSecurityPolicy* policy =
diff --git a/webkit/browser/fileapi/external_mount_points.cc b/webkit/browser/fileapi/external_mount_points.cc
index 1924c56..3acfd7f 100644
--- a/webkit/browser/fileapi/external_mount_points.cc
+++ b/webkit/browser/fileapi/external_mount_points.cc
@@ -149,6 +149,7 @@ bool ExternalMountPoints::CrackVirtualPath(
     const base::FilePath& virtual_path,
     std::string* mount_name,
     FileSystemType* type,
+    std::string* cracked_id,
     base::FilePath* path,
     FileSystemMountOption* mount_option) const {
   DCHECK(mount_name);
@@ -294,18 +295,20 @@ FileSystemURL ExternalMountPoints::CrackFileSystemURL(
 
   std::string mount_name;
   FileSystemType cracked_type;
+  std::string cracked_id;
   base::FilePath cracked_path;
   FileSystemMountOption cracked_mount_option;
 
   if (!CrackVirtualPath(virtual_path, &mount_name, &cracked_type,
-                        &cracked_path, &cracked_mount_option)) {
+                        &cracked_id, &cracked_path, &cracked_mount_option)) {
     return FileSystemURL();
   }
 
   return FileSystemURL(
       url.origin(), url.mount_type(), url.virtual_path(),
       !url.filesystem_id().empty() ? url.filesystem_id() : mount_name,
-      cracked_type, cracked_path, mount_name, cracked_mount_option);
+      cracked_type, cracked_path,
+      cracked_id.empty() ? mount_name : cracked_id, cracked_mount_option);
 }
 
 bool ExternalMountPoints::ValidateNewMountPoint(const std::string& mount_name,
diff --git a/webkit/browser/fileapi/external_mount_points.h b/webkit/browser/fileapi/external_mount_points.h
index fefa6fe..7891375 100644
--- a/webkit/browser/fileapi/external_mount_points.h
+++ b/webkit/browser/fileapi/external_mount_points.h
@@ -73,6 +73,7 @@ class WEBKIT_STORAGE_BROWSER_EXPORT ExternalMountPoints
       const base::FilePath& virtual_path,
       std::string* mount_name,
       FileSystemType* type,
+      std::string* cracked_id,
       base::FilePath* path,
       FileSystemMountOption* mount_option) const OVERRIDE;
   virtual FileSystemURL CrackURL(const GURL& url) const OVERRIDE;
diff --git a/webkit/browser/fileapi/isolated_context.cc b/webkit/browser/fileapi/isolated_context.cc
index f126330..a187a05 100644
--- a/webkit/browser/fileapi/isolated_context.cc
+++ b/webkit/browser/fileapi/isolated_context.cc
@@ -106,7 +106,9 @@ class IsolatedContext::Instance {
   // IsolatedContext::RegisterFileSystemForPath() or
   // IsolatedContext::RegisterFileSystemForVirtualPath().
   // Most of isolated file system contexts should be of this type.
-  Instance(FileSystemType type, const MountPointInfo& file_info,
+  Instance(FileSystemType type,
+           const std::string& filesystem_id,
+           const MountPointInfo& file_info,
            PathType path_type);
 
   // For a multi-paths isolated file system.  As of writing only file system
@@ -117,6 +119,7 @@ class IsolatedContext::Instance {
   ~Instance();
 
   FileSystemType type() const { return type_; }
+  const std::string& filesystem_id() const { return filesystem_id_; }
   const MountPointInfo& file_info() const { return file_info_; }
   const std::set<MountPointInfo>& files() const { return files_; }
   int ref_counts() const { return ref_counts_; }
@@ -131,6 +134,7 @@ class IsolatedContext::Instance {
 
  private:
   const FileSystemType type_;
+  const std::string filesystem_id_;
 
   // For single-path instance.
   const MountPointInfo file_info_;
@@ -147,9 +151,11 @@ class IsolatedContext::Instance {
 };
 
 IsolatedContext::Instance::Instance(FileSystemType type,
+                                    const std::string& filesystem_id,
                                     const MountPointInfo& file_info,
                                     Instance::PathType path_type)
     : type_(type),
+      filesystem_id_(filesystem_id),
       file_info_(file_info),
       path_type_(path_type),
       ref_counts_(0) {
@@ -218,6 +224,7 @@ std::string IsolatedContext::RegisterDraggedFileSystem(
 
 std::string IsolatedContext::RegisterFileSystemForPath(
     FileSystemType type,
+    const std::string& filesystem_id,
     const base::FilePath& path_in,
     std::string* register_name) {
   base::FilePath path(path_in.NormalizePathSeparators());
@@ -233,11 +240,12 @@ std::string IsolatedContext::RegisterFileSystemForPath(
   }
 
   base::AutoLock locker(lock_);
-  std::string filesystem_id = GetNewFileSystemId();
-  instance_map_[filesystem_id] = new Instance(type, MountPointInfo(name, path),
-                                              Instance::PLATFORM_PATH);
-  path_to_id_map_[path].insert(filesystem_id);
-  return filesystem_id;
+  std::string new_id = GetNewFileSystemId();
+  instance_map_[new_id] = new Instance(type, filesystem_id,
+                                       MountPointInfo(name, path),
+                                       Instance::PLATFORM_PATH);
+  path_to_id_map_[path].insert(new_id);
+  return new_id;
 }
 
 std::string IsolatedContext::RegisterFileSystemForVirtualPath(
@@ -251,6 +259,7 @@ std::string IsolatedContext::RegisterFileSystemForVirtualPath(
   std::string filesystem_id = GetNewFileSystemId();
   instance_map_[filesystem_id] = new Instance(
       type,
+      std::string(),  // filesystem_id
       MountPointInfo(register_name, cracked_path_prefix),
       Instance::VIRTUAL_PATH);
   path_to_id_map_[path].insert(filesystem_id);
@@ -281,6 +290,7 @@ bool IsolatedContext::CrackVirtualPath(
     const base::FilePath& virtual_path,
     std::string* id_or_name,
     FileSystemType* type,
+    std::string* cracked_id,
     base::FilePath* path,
     FileSystemMountOption* mount_option) const {
   DCHECK(id_or_name);
@@ -314,6 +324,8 @@ bool IsolatedContext::CrackVirtualPath(
     const Instance* instance = found_instance->second;
     if (type)
       *type = instance->type();
+    if (cracked_id)
+      *cracked_id = instance->filesystem_id();
 
     if (component_iter == components.end()) {
       // The virtual root case.
@@ -420,18 +432,22 @@ FileSystemURL IsolatedContext::CrackFileSystemURL(
     return FileSystemURL();
 
   std::string mount_name;
+  std::string cracked_mount_name;
   FileSystemType cracked_type;
   base::FilePath cracked_path;
   FileSystemMountOption cracked_mount_option;
   if (!CrackVirtualPath(url.path(), &mount_name, &cracked_type,
-                        &cracked_path, &cracked_mount_option)) {
+                        &cracked_mount_name, &cracked_path,
+                        &cracked_mount_option)) {
     return FileSystemURL();
   }
 
   return FileSystemURL(
       url.origin(), url.mount_type(), url.virtual_path(),
       !url.filesystem_id().empty() ? url.filesystem_id() : mount_name,
-      cracked_type, cracked_path, mount_name, cracked_mount_option);
+      cracked_type, cracked_path,
+      cracked_mount_name.empty() ? mount_name : cracked_mount_name,
+      cracked_mount_option);
 }
 
 bool IsolatedContext::UnregisterFileSystem(const std::string& filesystem_id) {
diff --git a/webkit/browser/fileapi/isolated_context.h b/webkit/browser/fileapi/isolated_context.h
index 2a4ae47..213082d 100644
--- a/webkit/browser/fileapi/isolated_context.h
+++ b/webkit/browser/fileapi/isolated_context.h
@@ -93,12 +93,13 @@ class WEBKIT_STORAGE_BROWSER_EXPORT IsolatedContext : public MountPoints {
   std::string RegisterDraggedFileSystem(const FileInfoSet& files);
 
   // Registers a new isolated filesystem for a given |path| of filesystem
-  // |type| filesystem and returns a new filesystem ID.
+  // |type| filesystem with |filesystem_id| and returns a new filesystem ID.
   // |path| must be an absolute path which has no parent references ('..').
   // If |register_name| is non-null and has non-empty string the path is
   // registered as the given |register_name|, otherwise it is populated
   // with the name internally assigned to the path.
   std::string RegisterFileSystemForPath(FileSystemType type,
+                                        const std::string& filesystem_id,
                                         const base::FilePath& path,
                                         std::string* register_name);
 
@@ -148,6 +149,7 @@ class WEBKIT_STORAGE_BROWSER_EXPORT IsolatedContext : public MountPoints {
       const base::FilePath& virtual_path,
       std::string* filesystem_id,
       FileSystemType* type,
+      std::string* cracked_id,
       base::FilePath* path,
       FileSystemMountOption* mount_option) const OVERRIDE;
   virtual FileSystemURL CrackURL(const GURL& url) const OVERRIDE;
diff --git a/webkit/browser/fileapi/mount_points.h b/webkit/browser/fileapi/mount_points.h
index 4ebf6e7..d206ab9 100644
--- a/webkit/browser/fileapi/mount_points.h
+++ b/webkit/browser/fileapi/mount_points.h
@@ -87,6 +87,7 @@ class WEBKIT_STORAGE_BROWSER_EXPORT MountPoints {
   virtual bool CrackVirtualPath(const base::FilePath& virtual_path,
                                 std::string* mount_name,
                                 FileSystemType* type,
+                                std::string* cracked_id,
                                 base::FilePath* path,
                                 FileSystemMountOption* mount_option) const = 0;