Refactor json automation interface for pyauto hooks.

Reduces the number of lines you need to add per new automation hook. Shaves
off several lines of code.

Refactor pyauto.py to obviate raising exception in case the json interfaces produces an error string.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=52054

Review URL: http://codereview.chromium.org/2898001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52628 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 318 insertions, 392 deletions

diff --git a/chrome/browser/automation/automation_provider.cc b/chrome/browser/automation/automation_provider.cc
index cbc6cd4..16d5090a 100644
--- a/chrome/browser/automation/automation_provider.cc
+++ b/chrome/browser/automation/automation_provider.cc
@@ -31,6 +31,7 @@
 #include "chrome/browser/app_modal_dialog_queue.h"
 #include "chrome/browser/autofill/autofill_manager.h"
 #include "chrome/browser/automation/automation_extension_tracker.h"
+#include "chrome/browser/automation/automation_provider_json.h"
 #include "chrome/browser/automation/automation_provider_list.h"
 #include "chrome/browser/automation/automation_provider_observers.h"
 #include "chrome/browser/automation/extension_port_container.h"
@@ -1714,9 +1715,7 @@ void AutomationProvider::SetWindowDimensions(Browser* browser,
   if (args->GetInteger(L"height", &height))
     rect.set_height(height);
   browser->window()->SetBounds(rect);
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, std::string("{}"), true);
-  Send(reply_message);
+  AutomationJSONReply(this, reply_message).SendSuccess(NULL);
 }
 
 // Sample json input: { "command": "GetBrowserInfo" }
@@ -1725,9 +1724,6 @@ void AutomationProvider::SetWindowDimensions(Browser* browser,
 void AutomationProvider::GetBrowserInfo(Browser* browser,
                                         DictionaryValue* args,
                                         IPC::Message* reply_message) {
-  std::string json_return;
-  bool reply_return = true;
-
   DictionaryValue* properties = new DictionaryValue;
   properties->SetString(L"ChromeVersion", chrome::kChromeVersion);
   properties->SetString(L"BrowserProcessExecutableName",
@@ -1838,11 +1834,7 @@ void AutomationProvider::GetBrowserInfo(Browser* browser,
     }
   }
   return_value->Set(L"extension_processes", extension_processes);
-
-  base::JSONWriter::Write(return_value.get(), false, &json_return);
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  AutomationJSONReply(this, reply_message).SendSuccess(return_value.get());
 }
 
 // Sample json input: { "command": "GetHistoryInfo",
@@ -1879,46 +1871,40 @@ void AutomationProvider::GetHistoryInfo(Browser* browser,
 void AutomationProvider::AddHistoryItem(Browser* browser,
                                         DictionaryValue* args,
                                         IPC::Message* reply_message) {
-  bool reply_return = true;
-  std::string json_return = "{}";
-
   DictionaryValue* item = NULL;
   args->GetDictionary(L"item", &item);
   string16 url_text;
   string16 title;
   base::Time time = base::Time::Now();
+  AutomationJSONReply reply(this, reply_message);
 
-  if (item->GetString("url", &url_text)) {
-    GURL gurl(url_text);
-    item->GetString("title", &title);  // Don't care if it fails.
-    int it;
-    double dt;
-    if (item->GetInteger(L"time", &it))
-      time = base::Time::FromTimeT(it);
-    else if (item->GetReal(L"time", &dt))
-      time = base::Time::FromDoubleT(dt);
-
-    // Ideas for "dummy" values (e.g. id_scope) came from
-    // chrome/browser/autocomplete/history_contents_provider_unittest.cc
-    HistoryService* hs = profile_->GetHistoryService(Profile::EXPLICIT_ACCESS);
-    const void* id_scope = reinterpret_cast<void*>(1);
-    hs->AddPage(gurl, time,
-                id_scope,
-                0,
-                GURL(),
-                PageTransition::LINK,
-                history::RedirectList(),
-                false);
-    if (title.length())
-      hs->SetPageTitle(gurl, title);
-  } else {
-    json_return = JSONErrorString("bad args (no URL in dict?)");
-    reply_return = false;
+  if (!item->GetString("url", &url_text)) {
+    reply.SendError("bad args (no URL in dict?)");
+    return;
   }
-
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  GURL gurl(url_text);
+  item->GetString("title", &title);  // Don't care if it fails.
+  int it;
+  double dt;
+  if (item->GetInteger(L"time", &it))
+    time = base::Time::FromTimeT(it);
+  else if (item->GetReal(L"time", &dt))
+    time = base::Time::FromDoubleT(dt);
+
+  // Ideas for "dummy" values (e.g. id_scope) came from
+  // chrome/browser/autocomplete/history_contents_provider_unittest.cc
+  HistoryService* hs = profile_->GetHistoryService(Profile::EXPLICIT_ACCESS);
+  const void* id_scope = reinterpret_cast<void*>(1);
+  hs->AddPage(gurl, time,
+              id_scope,
+              0,
+              GURL(),
+              PageTransition::LINK,
+              history::RedirectList(),
+              false);
+  if (title.length())
+    hs->SetPageTitle(gurl, title);
+  reply.SendSuccess(NULL);
 }
 
 // Sample json input: { "command": "GetDownloadsInfo" }
@@ -1926,22 +1912,20 @@ void AutomationProvider::AddHistoryItem(Browser* browser,
 void AutomationProvider::GetDownloadsInfo(Browser* browser,
                                           DictionaryValue* args,
                                           IPC::Message* reply_message) {
-  std::string json_return;
-  bool reply_return = true;
   AutomationProviderDownloadManagerObserver observer;
   std::vector<DownloadItem*> downloads;
   scoped_ptr<DictionaryValue> return_value(new DictionaryValue);
+  AutomationJSONReply reply(this, reply_message);
 
   if (!profile_->HasCreatedDownloadManager()) {
-    json_return = JSONErrorString("no download manager");
-    reply_return = false;
-  } else {
-    // Use DownloadManager's GetDownloads() method and not GetCurrentDownloads()
-    // since that would be transient; a download might enter and empty out
-    // the current download queue too soon to be noticed.
-    profile_->GetDownloadManager()->GetDownloads(&observer, L"");
-    downloads = observer.Downloads();
+    reply.SendError("no download manager");
+    return;
   }
+  // Use DownloadManager's GetDownloads() method and not GetCurrentDownloads()
+  // since that would be transient; a download might enter and empty out
+  // the current download queue too soon to be noticed.
+  profile_->GetDownloadManager()->GetDownloads(&observer, L"");
+  downloads = observer.Downloads();
 
   std::map<DownloadItem::DownloadState, std::string> state_to_string;
   state_to_string[DownloadItem::IN_PROGRESS] = std::string("IN_PROGRESS");
@@ -1979,11 +1963,8 @@ void AutomationProvider::GetDownloadsInfo(Browser* browser,
     list_of_downloads->Append(dl_item_value);
   }
   return_value->Set(L"downloads", list_of_downloads);
-  base::JSONWriter::Write(return_value.get(), false, &json_return);
 
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  reply.SendSuccess(return_value.get());
   // All value objects allocated above are owned by |return_value|
   // and get freed by it.
 }
@@ -1992,27 +1973,19 @@ void AutomationProvider::WaitForDownloadsToComplete(
     Browser* browser,
     DictionaryValue* args,
     IPC::Message* reply_message) {
-  std::string json_return;
-  bool reply_return = true;
   AutomationProviderDownloadManagerObserver observer;
   std::vector<DownloadItem*> downloads;
+  AutomationJSONReply reply(this, reply_message);
 
   // Look for a quick return.
   if (!profile_->HasCreatedDownloadManager()) {
-    json_return = JSONErrorString("no download manager");
-    reply_return = false;
-  } else {
-    profile_->GetDownloadManager()->GetCurrentDownloads(&observer,
-                                                        FilePath());
-    downloads = observer.Downloads();
-    if (downloads.size() == 0) {
-      json_return = "{}";
-    }
+    reply.SendSuccess(NULL);  // No download manager.
+    return;
   }
-  if (!json_return.empty()) {
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-        reply_message, json_return, reply_return);
-    Send(reply_message);
+  profile_->GetDownloadManager()->GetCurrentDownloads(&observer, FilePath());
+  downloads = observer.Downloads();
+  if (downloads.size() == 0) {
+    reply.SendSuccess(NULL);
     return;
   }
 
@@ -2033,9 +2006,6 @@ void AutomationProvider::WaitForDownloadsToComplete(
 void AutomationProvider::GetPrefsInfo(Browser* browser,
                                       DictionaryValue* args,
                                       IPC::Message* reply_message) {
-  std::string json_return;
-  bool reply_return = true;
-
   const PrefService::PreferenceSet& prefs =
       profile_->GetPrefs()->preference_set();
   DictionaryValue* items = new DictionaryValue;
@@ -2045,42 +2015,35 @@ void AutomationProvider::GetPrefsInfo(Browser* browser,
   }
   scoped_ptr<DictionaryValue> return_value(new DictionaryValue);
   return_value->Set(L"prefs", items);  // return_value owns items.
-
-  base::JSONWriter::Write(return_value.get(), false, &json_return);
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  AutomationJSONReply(this, reply_message).SendSuccess(return_value.get());
 }
 
 // Sample json input: { "command": "SetPrefs", "path": path, "value": value }
 void AutomationProvider::SetPrefs(Browser* browser,
                                   DictionaryValue* args,
                                   IPC::Message* reply_message) {
-  bool reply_return = true;
-  std::string json_return = "{}";
   std::wstring path;
   Value* val;
+  AutomationJSONReply reply(this, reply_message);
   if (args->GetString(L"path", &path) && args->Get(L"value", &val)) {
     PrefService* pref_service = profile_->GetPrefs();
     const PrefService::Preference* pref =
         pref_service->FindPreference(path.c_str());
     if (!pref) {  // Not a registered pref.
-      json_return = JSONErrorString("pref not registered.");
-      reply_return = false;
+      reply.SendError("pref not registered.");
+      return;
     } else if (pref->IsManaged()) {  // Do not attempt to change a managed pref.
-      json_return = JSONErrorString("pref is managed. cannot be changed.");
-      reply_return = false;
+      reply.SendError("pref is managed. cannot be changed.");
+      return;
     } else {  // Set the pref.
       pref_service->Set(path.c_str(), *val);
     }
   } else {
-    json_return = JSONErrorString("no pref path or value given.");
-    reply_return = false;
+    reply.SendError("no pref path or value given.");
+    return;
   }
 
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  reply.SendSuccess(NULL);
 }
 
 // Sample json input: { "command": "GetOmniboxInfo" }
@@ -2088,8 +2051,6 @@ void AutomationProvider::SetPrefs(Browser* browser,
 void AutomationProvider::GetOmniboxInfo(Browser* browser,
                                         DictionaryValue* args,
                                         IPC::Message* reply_message) {
-  std::string json_return;
-  bool reply_return = true;
   scoped_ptr<DictionaryValue> return_value(new DictionaryValue);
 
   LocationBar* loc_bar = browser->window()->GetLocationBar();
@@ -2120,10 +2081,7 @@ void AutomationProvider::GetOmniboxInfo(Browser* browser,
   properties->SetString(L"text", edit_view->GetText());
   return_value->Set(L"properties", properties);
 
-  base::JSONWriter::Write(return_value.get(), false, &json_return);
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  AutomationJSONReply(this, reply_message).SendSuccess(return_value.get());
 }
 
 // Sample json input: { "command": "SetOmniboxText",
@@ -2131,24 +2089,18 @@ void AutomationProvider::GetOmniboxInfo(Browser* browser,
 void AutomationProvider::SetOmniboxText(Browser* browser,
                                         DictionaryValue* args,
                                         IPC::Message* reply_message) {
-  std::string json_return = "{}";
-  bool reply_return = true;
   std::wstring text;
-
+  AutomationJSONReply reply(this, reply_message);
   if (!args->GetString(L"text", &text)) {
-    json_return = JSONErrorString("text missing");
-    reply_return = false;
-  } else {
-    browser->FocusLocationBar();
-    LocationBar* loc_bar = browser->window()->GetLocationBar();
-    AutocompleteEditView* edit_view = loc_bar->location_entry();
-    edit_view->model()->OnSetFocus(false);
-    edit_view->SetUserText(text);
+    reply.SendError("text missing");
+    return;
   }
-
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  browser->FocusLocationBar();
+  LocationBar* loc_bar = browser->window()->GetLocationBar();
+  AutocompleteEditView* edit_view = loc_bar->location_entry();
+  edit_view->model()->OnSetFocus(false);
+  edit_view->SetUserText(text);
+  reply.SendSuccess(NULL);
 }
 
 // Sample json input: { "command": "OmniboxMovePopupSelection",
@@ -2159,22 +2111,16 @@ void AutomationProvider::OmniboxMovePopupSelection(
     Browser* browser,
     DictionaryValue* args,
     IPC::Message* reply_message) {
-  std::string json_return = "{}";
-  bool reply_return = true;
   int count;
-
+  AutomationJSONReply reply(this, reply_message);
   if (!args->GetInteger(L"count", &count)) {
-    json_return = JSONErrorString("count missing");
-    reply_return = false;
-  } else {
-    LocationBar* loc_bar = browser->window()->GetLocationBar();
-    AutocompleteEditModel* model = loc_bar->location_entry()->model();
-    model->OnUpOrDownKeyPressed(count);
+    reply.SendError("count missing");
+    return;
   }
-
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  LocationBar* loc_bar = browser->window()->GetLocationBar();
+  AutocompleteEditModel* model = loc_bar->location_entry()->model();
+  model->OnUpOrDownKeyPressed(count);
+  reply.SendSuccess(NULL);
 }
 
 // Sample json input: { "command": "OmniboxAcceptInput" }
@@ -2212,9 +2158,6 @@ void AutomationProvider::GetInitialLoadTimes(
 void AutomationProvider::GetPluginsInfo(Browser* browser,
                                         DictionaryValue* args,
                                         IPC::Message* reply_message) {
-  std::string json_return;
-  bool reply_return = true;
-
   std::vector<WebPluginInfo> plugins;
   NPAPI::PluginList::Singleton()->GetPlugins(false, &plugins);
   ListValue* items = new ListValue;
@@ -2254,10 +2197,7 @@ void AutomationProvider::GetPluginsInfo(Browser* browser,
   scoped_ptr<DictionaryValue> return_value(new DictionaryValue);
   return_value->Set(L"plugins", items);  // return_value owns items.
 
-  base::JSONWriter::Write(return_value.get(), false, &json_return);
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  AutomationJSONReply(this, reply_message).SendSuccess(return_value.get());
 }
 
 // Sample json input:
@@ -2266,21 +2206,17 @@ void AutomationProvider::GetPluginsInfo(Browser* browser,
 void AutomationProvider::EnablePlugin(Browser* browser,
                                       DictionaryValue* args,
                                       IPC::Message* reply_message) {
-  std::string json_return = "{}";
-  bool reply_return = true;
   FilePath::StringType path;
+  AutomationJSONReply reply(this, reply_message);
   if (!args->GetString(L"path", &path)) {
-    json_return = JSONErrorString("path not specified.");
-    reply_return = false;
+    reply.SendError("path not specified.");
+    return;
   } else if (!NPAPI::PluginList::Singleton()->EnablePlugin(FilePath(path))) {
-    json_return = StringPrintf("{\"error\": \"Could not enable plugin"
-                               " for path %s.\"}", path.c_str());
-    reply_return = false;
+    reply.SendError(StringPrintf("Could not enable plugin for path %s.",
+                                 path.c_str()));
+    return;
   }
-
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  reply.SendSuccess(NULL);
 }
 
 // Sample json input:
@@ -2289,21 +2225,17 @@ void AutomationProvider::EnablePlugin(Browser* browser,
 void AutomationProvider::DisablePlugin(Browser* browser,
                                        DictionaryValue* args,
                                        IPC::Message* reply_message) {
-  std::string json_return = "{}";
-  bool reply_return = true;
   FilePath::StringType path;
+  AutomationJSONReply reply(this, reply_message);
   if (!args->GetString(L"path", &path)) {
-    json_return = JSONErrorString("path not specified.");
-    reply_return = false;
+    reply.SendError("path not specified.");
+    return;
   } else if (!NPAPI::PluginList::Singleton()->DisablePlugin(FilePath(path))) {
-    json_return = StringPrintf("{\"error\": \"Could not enable plugin"
-                               " for path %s.\"}", path.c_str());
-    reply_return = false;
+    reply.SendError(StringPrintf("Could not disable plugin for path %s.",
+                                 path.c_str()));
+    return;
   }
-
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  reply.SendSuccess(NULL);
 }
 
 // Sample json input:
@@ -2315,41 +2247,34 @@ void AutomationProvider::DisablePlugin(Browser* browser,
 void AutomationProvider::SaveTabContents(Browser* browser,
                                          DictionaryValue* args,
                                          IPC::Message* reply_message) {
-  std::string json_return;
   int tab_index = 0;
   FilePath::StringType filename;
   FilePath::StringType parent_directory;
   TabContents* tab_contents = NULL;
+  AutomationJSONReply reply(this, reply_message);
 
   if (!args->GetInteger(L"tab_index", &tab_index) ||
       !args->GetString(L"filename", &filename)) {
-    json_return = JSONErrorString("tab_index or filename param missing");
+    reply.SendError("tab_index or filename param missing");
+    return;
   } else {
     tab_contents = browser->GetTabContentsAt(tab_index);
     if (!tab_contents) {
-      json_return = JSONErrorString("no tab at tab_index");
-    }
-  }
-  if (tab_contents) {
-    // We're doing a SAVE_AS_ONLY_HTML so the the directory path isn't
-    // used.  Nevertheless, SavePackage requires it be valid.  Sigh.
-    parent_directory = FilePath(filename).DirName().value();
-    if (!tab_contents->SavePage(FilePath(filename), FilePath(parent_directory),
-                                SavePackage::SAVE_AS_ONLY_HTML)) {
-      json_return = JSONErrorString("Could not initiate SavePage");
-    } else {
-      // The observer will delete itself when done.
-      new SavePackageNotificationObserver(tab_contents->save_package(),
-                                          this, reply_message);
+      reply.SendError("no tab at tab_index");
       return;
     }
   }
-
-  // If we get here, error.
-  DCHECK(!json_return.empty());
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, false);
-  Send(reply_message);
+  // We're doing a SAVE_AS_ONLY_HTML so the the directory path isn't
+  // used.  Nevertheless, SavePackage requires it be valid.  Sigh.
+  parent_directory = FilePath(filename).DirName().value();
+  if (!tab_contents->SavePage(FilePath(filename), FilePath(parent_directory),
+                              SavePackage::SAVE_AS_ONLY_HTML)) {
+    reply.SendError("Could not initiate SavePage");
+    return;
+  }
+  // The observer will delete itself when done.
+  new SavePackageNotificationObserver(tab_contents->save_package(),
+                                      this, reply_message);
 }
 
 // Refer to ImportSettings() in chrome/test/pyautolib/pyauto.py for sample
@@ -2358,8 +2283,6 @@ void AutomationProvider::SaveTabContents(Browser* browser,
 void AutomationProvider::ImportSettings(Browser* browser,
                                         DictionaryValue* args,
                                         IPC::Message* reply_message) {
-  std::string json_return = "{}";
-
   // Map from the json string passed over to the import item masks.
   std::map<std::string, ImportItem> string_to_import_item;
   string_to_import_item["HISTORY"] = importer::HISTORY;
@@ -2378,11 +2301,8 @@ void AutomationProvider::ImportSettings(Browser* browser,
   if (!args->GetString(L"import_from", &browser_name) ||
       !args->GetBoolean(L"first_run", &first_run) ||
       !args->GetList(L"import_items", &import_items_list)) {
-    std::string json_return =
-        JSONErrorString("Incorrect type for one or more of the arguments.");
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-        reply_message, json_return, false);
-    Send(reply_message);
+    AutomationJSONReply(this, reply_message).SendError(
+        "Incorrect type for one or more of the arguments.");
     return;
   }
 
@@ -2392,11 +2312,8 @@ void AutomationProvider::ImportSettings(Browser* browser,
     import_items_list->GetString(i, &item);
     // If the provided string is not part of the map, error out.
     if (!ContainsKey(string_to_import_item, item)) {
-      json_return =
-          JSONErrorString("Invalid item string found in import_items.");
-      AutomationMsg_SendJSONRequest::WriteReplyParams(
-          reply_message, json_return, false);
-      Send(reply_message);
+      AutomationJSONReply(this, reply_message).SendError(
+          "Invalid item string found in import_items.");
       return;
     }
     import_items |= string_to_import_item[item];
@@ -2416,11 +2333,8 @@ void AutomationProvider::ImportSettings(Browser* browser,
   }
   // If we made it to the end of the loop, then the input was bad.
   if (i == num_browsers) {
-    json_return =
-        JSONErrorString("Invalid browser name string found.");
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-        reply_message, json_return, false);
-    Send(reply_message);
+    AutomationJSONReply(this, reply_message).SendError(
+        "Invalid browser name string found.");
     return;
   }
 
@@ -2438,8 +2352,6 @@ void AutomationProvider::ImportSettings(Browser* browser,
 void AutomationProvider::ClearBrowsingData(Browser* browser,
                                            DictionaryValue* args,
                                            IPC::Message* reply_message) {
-  std::string json_return = "{}";
-
   std::map<std::string, BrowsingDataRemover::TimePeriod> string_to_time_period;
   string_to_time_period["LAST_HOUR"] = BrowsingDataRemover::LAST_HOUR;
   string_to_time_period["LAST_DAY"] = BrowsingDataRemover::LAST_DAY;
@@ -2459,12 +2371,8 @@ void AutomationProvider::ClearBrowsingData(Browser* browser,
   ListValue* to_remove;
   if (!args->GetString(L"time_period", &time_period) ||
       !args->GetList(L"to_remove", &to_remove)) {
-    // TODO(nirnimesh): Here and below refactor returns with pending CL.
-    std::string json_return =
-         JSONErrorString("time_period must be a string and to_remove a list.");
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-         reply_message, json_return, false);
-    Send(reply_message);
+    AutomationJSONReply(this, reply_message).SendError(
+        "time_period must be a string and to_remove a list.");
     return;
   }
 
@@ -2475,22 +2383,16 @@ void AutomationProvider::ClearBrowsingData(Browser* browser,
     to_remove->GetString(i, &removal);
     // If the provided string is not part of the map, then error out.
     if (!ContainsKey(string_to_mask_value, removal)) {
-      std::string json_return =
-          JSONErrorString("Invalid browsing data string found in to_remove.");
-      AutomationMsg_SendJSONRequest::WriteReplyParams(
-          reply_message, json_return, false);
-      Send(reply_message);
+      AutomationJSONReply(this, reply_message).SendError(
+          "Invalid browsing data string found in to_remove.");
       return;
     }
     remove_mask |= string_to_mask_value[removal];
   }
 
   if (!ContainsKey(string_to_time_period, time_period)) {
-    std::string json_return =
-        JSONErrorString("Invalid string for time_period.");
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-        reply_message, json_return, false);
-    Send(reply_message);
+    AutomationJSONReply(this, reply_message).SendError(
+        "Invalid string for time_period.");
     return;
   }
 
@@ -2517,12 +2419,7 @@ void AutomationProvider::GetThemeInfo(Browser* browser,
     return_value->Set(L"colors", theme->GetThemeColors()->DeepCopy());
     return_value->Set(L"tints", theme->GetThemeTints()->DeepCopy());
   }
-
-  std::string json_return;
-  base::JSONWriter::Write(return_value.get(), false, &json_return);
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, true);
-  Send(reply_message);
+  AutomationJSONReply(this, reply_message).SendSuccess(return_value.get());
 }
 
 // Sample json input:
@@ -2532,13 +2429,11 @@ void AutomationProvider::GetThemeInfo(Browser* browser,
 void AutomationProvider::GetAutoFillProfile(Browser* browser,
                                             DictionaryValue* args,
                                             IPC::Message* reply_message) {
-  std::string json_return;
-  bool reply_return = true;
-
   // Get the AutoFillProfiles currently in the database.
   int tab_index = 0;
   args->GetInteger(L"tab_index", &tab_index);
   TabContents* tab_contents = browser->GetTabContentsAt(tab_index);
+  AutomationJSONReply reply(this, reply_message);
 
   if (tab_contents) {
     PersonalDataManager* pdm = tab_contents->profile()->GetOriginalProfile()
@@ -2554,20 +2449,15 @@ void AutomationProvider::GetAutoFillProfile(Browser* browser,
 
       return_value->Set(L"profiles", profiles);
       return_value->Set(L"credit_cards", cards);
-
-      base::JSONWriter::Write(return_value.get(), false, &json_return);
+      reply.SendSuccess(return_value.get());
     } else {
-      json_return = JSONErrorString("No PersonalDataManager.");
-      reply_return = false;
+      reply.SendError("No PersonalDataManager.");
+      return;
     }
   } else {
-    json_return = JSONErrorString("No tab at that index.");
-    reply_return = false;
+    reply.SendError("No tab at that index.");
+    return;
   }
-
-  AutomationMsg_SendJSONRequest::WriteReplyParams(reply_message, json_return,
-                                                  reply_return);
-  Send(reply_message);
 }
 
 // Refer to FillAutoFillProfile() in chrome/test/pyautolib/pyauto.py for sample
@@ -2576,23 +2466,26 @@ void AutomationProvider::GetAutoFillProfile(Browser* browser,
 void AutomationProvider::FillAutoFillProfile(Browser* browser,
                                              DictionaryValue* args,
                                              IPC::Message* reply_message) {
-  std::string json_return = "{}";
-  bool reply_return = true;
-
+  AutomationJSONReply reply(this, reply_message);
   ListValue* profiles = NULL;
   ListValue* cards = NULL;
   args->GetList(L"profiles", &profiles);
   args->GetList(L"credit_cards", &cards);
+  std::string error_mesg;
 
   std::vector<AutoFillProfile> autofill_profiles;
   std::vector<CreditCard> credit_cards;
   // Create an AutoFillProfile for each of the dictionary profiles.
   if (profiles) {
-    autofill_profiles = GetAutoFillProfilesFromList(*profiles, &json_return);
+    autofill_profiles = GetAutoFillProfilesFromList(*profiles, &error_mesg);
   }
   // Create a CreditCard for each of the dictionary values.
   if (cards) {
-    credit_cards = GetCreditCardsFromList(*cards, &json_return);
+    credit_cards = GetCreditCardsFromList(*cards, &error_mesg);
+  }
+  if (!error_mesg.empty()) {
+    reply.SendError(error_mesg);
+    return;
   }
 
   // Save the AutoFillProfiles.
@@ -2607,16 +2500,14 @@ void AutomationProvider::FillAutoFillProfile(Browser* browser,
       pdm->OnAutoFillDialogApply(profiles? &autofill_profiles : NULL,
                                  cards? &credit_cards : NULL);
     } else {
-      json_return = JSONErrorString("No PersonalDataManager.");
-      reply_return = false;
+      reply.SendError("No PersonalDataManager.");
+      return;
     }
   } else {
-    json_return = JSONErrorString("No tab at that index.");
-    reply_return = false;
+    reply.SendError("No tab at that index.");
+    return;
   }
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_return, reply_return);
-  Send(reply_message);
+  reply.SendSuccess(NULL);
 }
 
 /* static */
@@ -2678,7 +2569,7 @@ ListValue* AutomationProvider::GetListFromCreditCards(
 
 /* static */
 std::vector<AutoFillProfile> AutomationProvider::GetAutoFillProfilesFromList(
-    const ListValue& profiles, std::string* json_return) {
+    const ListValue& profiles, std::string* error_message) {
   std::vector<AutoFillProfile> autofill_profiles;
   DictionaryValue* profile_info = NULL;
   string16 profile_label;
@@ -2701,7 +2592,7 @@ std::vector<AutoFillProfile> AutomationProvider::GetAutoFillProfilesFromList(
         if (profile_info->GetStringAsUTF16(type_it->second, &current_value)) {
           profile.SetInfo(AutoFillType(type_it->first), current_value);
         } else {
-          *json_return = JSONErrorString("All values must be strings");
+          *error_message= "All values must be strings";
           break;
         }
       }
@@ -2713,7 +2604,7 @@ std::vector<AutoFillProfile> AutomationProvider::GetAutoFillProfilesFromList(
 
 /* static */
 std::vector<CreditCard> AutomationProvider::GetCreditCardsFromList(
-    const ListValue& cards, std::string* json_return) {
+    const ListValue& cards, std::string* error_message) {
   std::vector<CreditCard> credit_cards;
   DictionaryValue* card_info = NULL;
   string16 card_label;
@@ -2735,7 +2626,7 @@ std::vector<CreditCard> AutomationProvider::GetCreditCardsFromList(
         if (card_info->GetStringAsUTF16(type_it->second, &current_value)) {
           card.SetInfo(AutoFillType(type_it->first), current_value);
         } else {
-          *json_return = JSONErrorString("All values must be strings");
+          *error_message= "All values must be strings";
           break;
         }
       }
@@ -2779,51 +2670,41 @@ std::map<AutoFillFieldType, std::wstring>
   return credit_card_type_to_string;
 }
 
-/* static */
-std::string AutomationProvider::JSONErrorString(const std::string& err) {
-  std::string prefix = "{\"error\": \"";
-  std::string no_quote_err;
-  std::string suffix = "\"}";
-
-  base::JsonDoubleQuote(err, false, &no_quote_err);
-  return prefix + no_quote_err + suffix;
-}
-
 void AutomationProvider::SendJSONRequest(int handle,
                                          std::string json_request,
                                          IPC::Message* reply_message) {
   Browser* browser = NULL;
-  std::string error_string;
   scoped_ptr<Value> values;
+  AutomationJSONReply reply(this, reply_message);
 
   // Basic error checking.
   if (browser_tracker_->ContainsHandle(handle)) {
     browser = browser_tracker_->GetResource(handle);
   }
   if (!browser) {
-    error_string = "no browser object";
-  } else {
-    base::JSONReader reader;
-    std::string error;
-    values.reset(reader.ReadAndReturnError(json_request, true, NULL, &error));
-    if (!error.empty()) {
-      error_string = error;
-    }
+    reply.SendError("no browser object");
+    return;
+  }
+  base::JSONReader reader;
+  std::string error;
+  values.reset(reader.ReadAndReturnError(json_request, true, NULL, &error));
+  if (!error.empty()) {
+    reply.SendError(error);
+    return;
   }
 
   // Make sure input is a dict with a string command.
   std::string command;
   DictionaryValue* dict_value = NULL;
-  if (error_string.empty()) {
-    if (values->GetType() != Value::TYPE_DICTIONARY) {
-      error_string = "not a dict or no command key in dict";
-    } else {
-      // Ownership remains with "values" variable.
-      dict_value = static_cast<DictionaryValue*>(values.get());
-      if (!dict_value->GetStringASCII(std::string("command"), &command)) {
-        error_string = "no command key in dict or not a string command";
-      }
-    }
+  if (values->GetType() != Value::TYPE_DICTIONARY) {
+    reply.SendError("not a dict");
+    return;
+  }
+  // Ownership remains with "values" variable.
+  dict_value = static_cast<DictionaryValue*>(values.get());
+  if (!dict_value->GetStringASCII(std::string("command"), &command)) {
+    reply.SendError("no command key in dict or not a string command");
+    return;
   }
 
   // Map json commands to their handlers.
@@ -2833,6 +2714,7 @@ void AutomationProvider::SendJSONRequest(int handle,
   handler_map["GetPluginsInfo"] = &AutomationProvider::GetPluginsInfo;
 
   handler_map["GetBrowserInfo"] = &AutomationProvider::GetBrowserInfo;
+
   handler_map["GetHistoryInfo"] = &AutomationProvider::GetHistoryInfo;
   handler_map["AddHistoryItem"] = &AutomationProvider::AddHistoryItem;
 
@@ -2865,35 +2747,16 @@ void AutomationProvider::SendJSONRequest(int handle,
   handler_map["GetAutoFillProfile"] = &AutomationProvider::GetAutoFillProfile;
   handler_map["FillAutoFillProfile"] = &AutomationProvider::FillAutoFillProfile;
 
-  if (error_string.empty()) {
-    if (handler_map.find(std::string(command)) != handler_map.end()) {
-      (this->*handler_map[command])(browser, dict_value, reply_message);
-      return;
-    } else {
-      error_string = "Unknown command. Options: ";
-      for (std::map<std::string, JsonHandler>::const_iterator it =
-           handler_map.begin(); it != handler_map.end(); ++it) {
-        error_string += it->first + ", ";
-      }
-    }
-  }
-
-  // If we hit an error, return info.
-  // Return a dict of {"error", "descriptive_string_for_error"}.
-  // Else return an empty dict.
-  std::string json_string;
-  bool success = true;
-  if (!error_string.empty()) {
-    scoped_ptr<DictionaryValue> dict(new DictionaryValue);
-    dict->SetString(L"error", error_string);
-    base::JSONWriter::Write(dict.get(), false, &json_string);
-    success = false;
+  if (handler_map.find(std::string(command)) != handler_map.end()) {
+    (this->*handler_map[command])(browser, dict_value, reply_message);
   } else {
-    json_string = "{}";
+    std::string error_string = "Unknown command. Options: ";
+    for (std::map<std::string, JsonHandler>::const_iterator it =
+         handler_map.begin(); it != handler_map.end(); ++it) {
+      error_string += it->first + ", ";
+    }
+    reply.SendError(error_string);
   }
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message, json_string, success);
-  Send(reply_message);
 }
 
 void AutomationProvider::HandleInspectElementRequest(
diff --git a/chrome/browser/automation/automation_provider.h b/chrome/browser/automation/automation_provider.h
index a0d2dd7..524fd62 100644
--- a/chrome/browser/automation/automation_provider.h
+++ b/chrome/browser/automation/automation_provider.h
@@ -476,11 +476,11 @@ class AutomationProvider : public base::RefCounted<AutomationProvider>,
   // data structure used in the browser.
   // Args:
   //   profiles/cards: the ListValue of profiles/credit cards to translate.
-  //   json_return: a pointer to the return string in case of error.
+  //   error_message: a pointer to the return string in case of error.
   static std::vector<AutoFillProfile> GetAutoFillProfilesFromList(
-      const ListValue& profiles, std::string* json_return);
+      const ListValue& profiles, std::string* error_message);
   static std::vector<CreditCard> GetCreditCardsFromList(
-      const ListValue& cards, std::string* json_return);
+      const ListValue& cards, std::string* error_message);
 
   // The opposite of the above: translates from the internal data structure
   // for profiles and credit cards to a ListValue of DictionaryValues. The
@@ -497,10 +497,6 @@ class AutomationProvider : public base::RefCounted<AutomationProvider>,
   static std::map<AutoFillFieldType, std::wstring>
       GetCreditCardFieldToStringMap();
 
-  // Util for creating a JSON error return string (dict with key
-  // 'error' and error string value).  No need to quote input.
-  static std::string JSONErrorString(const std::string& err);
-
   // Generic pattern for pyautolib
   // Uses the JSON interface for input/output.
   void SendJSONRequest(int handle,
diff --git a/chrome/browser/automation/automation_provider_json.cc b/chrome/browser/automation/automation_provider_json.cc
new file mode 100644
index 0000000..05f3a1b
--- /dev/null
+++ b/chrome/browser/automation/automation_provider_json.cc
@@ -0,0 +1,55 @@
+// Copyright (c) 2010 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/automation/automation_provider_json.h"
+
+#include "base/json/json_writer.h"
+#include "base/json/string_escape.h"
+#include "chrome/test/automation/automation_messages.h"
+
+namespace {
+
+// Util for creating a JSON error return string (dict with key
+// 'error' and error string value).  No need to quote input.
+std::string JSONErrorString(const std::string& err) {
+  std::string prefix = "{\"error\": \"";
+  std::string no_quote_err;
+  std::string suffix = "\"}";
+
+  base::JsonDoubleQuote(err, false, &no_quote_err);
+  return prefix + no_quote_err + suffix;
+}
+
+}  // namespace
+
+AutomationJSONReply::AutomationJSONReply(AutomationProvider* provider,
+                                         IPC::Message* reply_message)
+  : provider_(provider),
+    message_(reply_message) {
+}
+
+AutomationJSONReply::~AutomationJSONReply() {
+  DCHECK(!message_) << "JSON automation request not replied!";
+}
+
+void AutomationJSONReply::SendSuccess(const Value* value) {
+  DCHECK(message_) << "Resending reply for JSON automation request";
+  std::string json_string = "{}";
+  if (value)
+    base::JSONWriter::Write(value, false, &json_string);
+  AutomationMsg_SendJSONRequest::WriteReplyParams(
+      message_, json_string, true);
+  provider_->Send(message_);
+  message_ = NULL;
+}
+
+void AutomationJSONReply::SendError(const std::string& error_message) {
+  DCHECK(message_) << "Resending reply for JSON automation request";
+  std::string json_string = JSONErrorString(error_message);
+  AutomationMsg_SendJSONRequest::WriteReplyParams(
+      message_, json_string, false);
+  provider_->Send(message_);
+  message_ = NULL;
+}
+
diff --git a/chrome/browser/automation/automation_provider_json.h b/chrome/browser/automation/automation_provider_json.h
new file mode 100644
index 0000000..a203c58
--- /dev/null
+++ b/chrome/browser/automation/automation_provider_json.h
@@ -0,0 +1,40 @@
+// Copyright (c) 2010 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.
+
+// Support utilities for the JSON automation interface used by PyAuto.
+
+#ifndef CHROME_BROWSER_AUTOMATION_AUTOMATION_PROVIDER_JSON_H_
+#define CHROME_BROWSER_AUTOMATION_AUTOMATION_PROVIDER_JSON_H_
+
+#include <string>
+
+#include "base/values.h"
+#include "ipc/ipc_message.h"
+#include "chrome/browser/automation/automation_provider.h"
+
+// Helper to ensure we always send a reply message for JSON automation requests.
+class AutomationJSONReply {
+ public:
+  // Creates a new reply object for the IPC message |reply_message| for
+  // |provider|. The caller is expected to call SendSuccess() or SendError()
+  // before destroying this object.
+  AutomationJSONReply(AutomationProvider* provider,
+                      IPC::Message* reply_message);
+
+  ~AutomationJSONReply();
+
+  // Send a success reply along with data contained in |value|.
+  // An empty message will be sent if |value| is NULL.
+  void SendSuccess(const Value* value);
+
+  // Send an error reply along with error message |error_message|.
+  void SendError(const std::string& error_message);
+
+ private:
+  AutomationProvider* provider_;
+  IPC::Message* message_;
+};
+
+#endif  // CHROME_BROWSER_AUTOMATION_AUTOMATION_PROVIDER_JSON_H_
+
diff --git a/chrome/browser/automation/automation_provider_observers.cc b/chrome/browser/automation/automation_provider_observers.cc
index 0076047..0745a90 100644
--- a/chrome/browser/automation/automation_provider_observers.cc
+++ b/chrome/browser/automation/automation_provider_observers.cc
@@ -9,6 +9,7 @@
 #include "base/string_util.h"
 #include "chrome/app/chrome_dll_resource.h"
 #include "chrome/browser/automation/automation_provider.h"
+#include "chrome/browser/automation/automation_provider_json.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
 #include "chrome/browser/dom_operation_notification_details.h"
 #include "chrome/browser/download/save_package.h"
@@ -974,9 +975,7 @@ void AutomationProviderDownloadItemObserver::OnDownloadFileCompleted(
     DownloadItem* download) {
   download->RemoveObserver(this);
   if (--downloads_ == 0) {
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-        reply_message_, std::string("{}"), true);
-    provider_->Send(reply_message_);
+    AutomationJSONReply(provider_, reply_message_).SendSuccess(NULL);
     delete this;
   }
 }
@@ -984,8 +983,6 @@ void AutomationProviderDownloadItemObserver::OnDownloadFileCompleted(
 void AutomationProviderHistoryObserver::HistoryQueryComplete(
     HistoryService::Handle request_handle,
     history::QueryResults* results) {
-  std::string json_return;
-  bool reply_return = true;
   scoped_ptr<DictionaryValue> return_value(new DictionaryValue);
 
   ListValue* history_list = new ListValue;
@@ -1005,26 +1002,20 @@ void AutomationProviderHistoryObserver::HistoryQueryComplete(
 
   return_value->Set(L"history", history_list);
   // Return history info.
-  base::JSONWriter::Write(return_value.get(), false, &json_return);
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message_, json_return, reply_return);
-  provider_->Send(reply_message_);
+  AutomationJSONReply reply(provider_, reply_message_);
+  reply.SendSuccess(return_value.get());
   delete this;
 }
 
 void AutomationProviderImportSettingsObserver::ImportEnded() {
   // Send back an empty success message.
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message_, std::string("{}"), true);
-  provider_->Send(reply_message_);
+  AutomationJSONReply(provider_, reply_message_).SendSuccess(NULL);
   delete this;
 }
 
 void AutomationProviderBrowsingDataObserver::OnBrowsingDataRemoverDone() {
   // Send back an empty success message
-  AutomationMsg_SendJSONRequest::WriteReplyParams(
-      reply_message_, std::string("{}"), true);
-  provider_->Send(reply_message_);
+  AutomationJSONReply(provider_, reply_message_).SendSuccess(NULL);
   delete this;
 }
 
@@ -1051,9 +1042,7 @@ void OmniboxAcceptNotificationObserver::Observe(
     const NotificationDetails& details) {
   if (type == NotificationType::LOAD_STOP ||
       type == NotificationType::AUTH_NEEDED) {
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-        reply_message_, std::string("{}"), false);
-    automation_->Send(reply_message_);
+    AutomationJSONReply(automation_, reply_message_).SendSuccess(NULL);
     delete this;
   } else {
     NOTREACHED();
@@ -1075,9 +1064,7 @@ void SavePackageNotificationObserver::Observe(
     const NotificationSource& source,
     const NotificationDetails& details) {
   if (type == NotificationType::SAVE_PACKAGE_SUCCESSFULLY_FINISHED) {
-    AutomationMsg_SendJSONRequest::WriteReplyParams(
-        reply_message_, std::string("{}"), true);
-    automation_->Send(reply_message_);
+    AutomationJSONReply(automation_, reply_message_).SendSuccess(NULL);
     delete this;
   } else {
     NOTREACHED();
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index 00fb53b..d9175e6 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -198,6 +198,8 @@
         'browser/automation/automation_provider_win.cc',
         'browser/automation/automation_provider.cc',
         'browser/automation/automation_provider.h',
+        'browser/automation/automation_provider_json.h',
+        'browser/automation/automation_provider_json.cc',
         'browser/automation/automation_provider_list.cc',
         'browser/automation/automation_provider_list_generic.cc',
         'browser/automation/automation_provider_list_mac.mm',
diff --git a/chrome/test/pyautolib/pyauto.py b/chrome/test/pyautolib/pyauto.py
index 72304d5..10a4504 100644
--- a/chrome/test/pyautolib/pyauto.py
+++ b/chrome/test/pyautolib/pyauto.py
@@ -28,7 +28,6 @@ to unittest.py
 import logging
 import optparse
 import os
-import re
 import shutil
 import sys
 import tempfile
@@ -260,6 +259,33 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       time.sleep(retry_sleep)
     return False
 
+  def _GetResultFromJSONRequest(self, cmd_dict, windex=0):
+    """Issue call over the JSON automation channel and fetch output.
+
+    This method packages the given dictionary into a json string, sends it
+    over the JSON automation channel, loads the json output string returned,
+    and returns it back as a dictionary.
+
+    Args:
+      cmd_dict: the command dictionary. It must have a 'command' key
+                Sample:
+                  {
+                    'command': 'SetOmniboxText',
+                    'text': text,
+                  }
+      windex: 0-based window index on which to work. Default: 0 (first window)
+
+    Returns:
+      a dictionary for the output returned by the automation channel.
+
+    Raises:
+      pyauto_errors.JSONInterfaceError if the automation call returns an error.
+    """
+    ret_dict = json.loads(self._SendJSONRequest(windex, json.dumps(cmd_dict)))
+    if ret_dict.has_key('error'):
+      raise JSONInterfaceError(ret_dict['error'])
+    return ret_dict
+
   def GetBookmarkModel(self):
     """Return the bookmark model as a BookmarkModel object.
 
@@ -318,9 +344,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
         'command': 'SetOmniboxText',
         'text': text,
     }
-    ret_dict = json.loads(self._SendJSONRequest(windex, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict, windex=windex)
 
   def WaitUntilOmniboxQueryDone(self, windex=0):
     """Wait until omnibox has finished populating results.
@@ -348,9 +372,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
         'command': 'OmniboxMovePopupSelection',
         'count': count,
     }
-    ret_dict = json.loads(self._SendJSONRequest(windex, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict, windex=windex)
 
   def OmniboxAcceptInput(self, windex=0):
     """Accepts the current string of text in the omnibox.
@@ -365,9 +387,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     cmd_dict = {
         'command': 'OmniboxAcceptInput',
     }
-    ret_dict = json.loads(self._SendJSONRequest(windex, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict, windex=windex)
 
   def GetPrefsInfo(self):
     """Return info about preferences.
@@ -409,16 +429,13 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       'path': path,
       'value': value,
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict)
 
   def WaitForAllDownloadsToComplete(self):
     """Wait for all downloads to complete."""
     # Implementation detail: uses the generic "JSON command" model
     # (experimental)
-    self._SendJSONRequest(0, json.dumps({'command':
-                                         'WaitForAllDownloadsToComplete'}))
+    self._GetResultFromJSONRequest({'command': 'WaitForAllDownloadsToComplete'})
 
   def DownloadAndWaitForStart(self, file_url):
     """Trigger download for the given url and wait for downloads to start.
@@ -461,10 +478,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       cmd_dict['width'] = width
     if height:
       cmd_dict['height'] = height
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
-    return ret_dict
+    self._GetResultFromJSONRequest(cmd_dict, windex=windex)
 
   def GetBrowserInfo(self):
     """Return info about the browser.
@@ -524,10 +538,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     cmd_dict = {  # Prepare command for the json interface
       'command': 'GetBrowserInfo',
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
-    return ret_dict
+    return self._GetResultFromJSONRequest(cmd_dict)
 
   def GetHistoryInfo(self, search_text=''):
     """Return info about browsing history.
@@ -626,10 +637,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       for credit_card in credit_cards:
         if not 'label' in credit_card:
           raise JSONInterfaceError('must specify label for all credit cards')
-    ret_dict = json.loads(self._SendJSONRequest(window_index,
-                                                json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict, windex=window_index)
 
   def GetAutoFillProfile(self, tab_index=0, window_index=0):
     """Return the profile including all profiles and credit cards currently
@@ -651,11 +659,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       'command': 'GetAutoFillProfile',
       'tab_index': tab_index
     }
-    ret_dict = json.loads(self._SendJSONRequest(window_index,
-                                                json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
-    return ret_dict
+    return self._GetResultFromJSONRequest(cmd_dict, windex=window_index)
 
   def AddHistoryItem(self, item):
     """Forge a history item for Chrome.
@@ -679,9 +683,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     }
     if not 'url' in item:
       raise JSONInterfaceError('must specify url')
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict)
 
   def GetPluginsInfo(self):
     """Return info about plugins.
@@ -706,9 +708,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       'command': 'EnablePlugin',
       'path': path,
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict)
 
   def DisablePlugin(self, path):
     """Disable the plugin at the given path.
@@ -722,9 +722,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       'command': 'DisablePlugin',
       'path': path,
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict)
 
   def GetTabContents(self, tab_index=0, window_index=0):
     """Get the html contents of a tab (a la "view source").
@@ -745,10 +743,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       'tab_index': tab_index,
       'filename': filename
     }
-    ret_dict = json.loads(self._SendJSONRequest(window_index,
-                                                json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
+    self._GetResultFromJSONRequest(cmd_dict, windex=window_index)
     try:
       f = open(filename)
       all_data = f.read()
@@ -787,10 +782,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       'first_run': first_run,
       'import_items': import_items
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
-    return ret_dict
+    return self._GetResultFromJSONRequest(cmd_dict)
 
   def ClearBrowsingData(self, to_remove, time_period):
     """Clear the specified browsing data. Implements the features available in
@@ -812,10 +804,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       'to_remove': to_remove,
       'time_period': time_period
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
-    return ret_dict
+    return self._GetResultFromJSONRequest(cmd_dict)
 
   def SetTheme(self, crx_file_path):
     """Installs the given theme synchronously.
@@ -843,10 +832,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     cmd_dict = {
       'command': 'ClearTheme',
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
-    return ret_dict
+    self._GetResultFromJSONRequest(cmd_dict)
 
   def GetThemeInfo(self):
     """Get info about theme.
@@ -874,10 +860,7 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     cmd_dict = {
       'command': 'GetThemeInfo',
     }
-    ret_dict = json.loads(self._SendJSONRequest(0, json.dumps(cmd_dict)))
-    if ret_dict.has_key('error'):
-      raise JSONInterfaceError(ret_dict['error'])
-    return ret_dict
+    return self._GetResultFromJSONRequest(cmd_dict)
 
 
 class PyUITestSuite(pyautolib.PyUITestSuiteBase, unittest.TestSuite):