Chrome Extensions chrome.experimental.offscreenTabs.* API implementation, docs, and test.

chrome/browser/extensions/extension_offscreen_tabs_module.cc

+// Copyright (c) 2011 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/extensions/extension_offscreen_tabs_module.h"
+
+#include <algorithm>
+#include <hash_map>
+#include <vector>
+
+#include "base/base64.h"
+#include "base/memory/ref_counted_memory.h"
+#include "base/stl_util.h"
+#include "base/string_number_conversions.h"
+#include "base/string_util.h"
+#include "base/stringprintf.h"
+#include "base/utf_string_conversions.h"
+#include "chrome/browser/extensions/extension_function_dispatcher.h"
+#include "chrome/browser/extensions/extension_host.h"
+#include "chrome/browser/extensions/extension_offscreen_tabs_module_constants.h"
+#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/extension_tabs_module.h"
+#include "chrome/browser/net/url_fixer_upper.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/sessions/restore_tab_helper.h"
+#include "chrome/browser/tabs/tab_strip_model.h"
+#include "chrome/browser/translate/translate_tab_helper.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_list.h"
+#include "chrome/browser/ui/browser_navigator.h"
+#include "chrome/browser/ui/browser_window.h"
+#include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
+#include "chrome/browser/ui/window_sizer.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/common/extensions/extension.h"
+#include "chrome/common/extensions/extension_error_utils.h"
+#include "chrome/common/extensions/extension_messages.h"
+#include "chrome/common/pref_names.h"
+#include "chrome/common/url_constants.h"
+#include "content/browser/renderer_host/backing_store.h"
+#include "content/browser/renderer_host/render_view_host.h"
+#include "content/browser/renderer_host/render_view_host_delegate.h"
+#include "content/browser/tab_contents/navigation_entry.h"
+#include "content/browser/tab_contents/tab_contents.h"
+#include "content/browser/tab_contents/tab_contents_view.h"
+#include "content/common/notification_service.h"
+#include "skia/ext/image_operations.h"
+#include "skia/ext/platform_canvas.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "ui/gfx/codec/jpeg_codec.h"
+#include "ui/gfx/codec/png_codec.h"
+
+using WebKit::WebInputEvent;
+
+namespace keys = extension_offscreen_tabs_module_constants;
+
+const int ToDataUrlOffscreenTabFunction::kDefaultQuality = 90;
+
+typedef base::hash_map<int, std::vector<TabContents*> > OffscreenTabsMap;
+OffscreenTabsMap* offscreen_tabs_map = new OffscreenTabsMap();

[Ken Russell (switch to Gerrit), 2011/08/23 22:46:53]

It's not OK to have a nontrivial initializer for this variable; it must be
initialized to NULL. Also, it needs to be in the anonymous namespace below. Add
a function like GetOffscreenTabsMap() which tests it for NULL, instantiates it
if so, and returns the new value, and call that function everywhere in this file
to fetch the map.

[alexbost, 2011/08/24 20:06:21]

Done.

+
+OffscreenTabsEventManager* event_manager;

[Ken Russell (switch to Gerrit), 2011/08/23 22:46:53]

Must go in the anonymous namespace as well. Also must be initialized to NULL.

[alexbost, 2011/08/24 20:06:21]

Done.

+
+namespace {
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+// Takes |url_string| and returns a GURL which is either valid and absolute
+// or invalid. If |url_string| is not directly interpretable as a valid (it is
+// likely a relative URL) an attempt is made to resolve it. |extension| is
+// provided so it can be resolved relative to its extension base
+// (chrome-extension://<id>/). Using the source frame url would be more correct,
+// but because the api shipped with urls resolved relative to their extension
+// base, we decided it wasn't worth breaking existing extensions to fix.
+GURL ResolvePossiblyRelativeURL(const std::string& url_string,
+                                const Extension* extension) {
+  GURL url = GURL(url_string);
+  if (!url.is_valid())
+    url = extension->GetResourceURL(url_string);
+
+  return url;
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+bool IsCrashURL(const GURL& url) {
+  // Check a fixed-up URL, to normalize the scheme and parse hosts correctly.
+  GURL fixed_url =
+      URLFixerUpper::FixupURL(url.possibly_invalid_spec(), std::string());
+  return (fixed_url.SchemeIs(chrome::kChromeUIScheme) &&
+          (fixed_url.host() == chrome::kChromeUIBrowserCrashHost ||
+           fixed_url.host() == chrome::kChromeUICrashHost));
+}
+
+bool GetOffscreenTabById(const int tab_id,
+                         TabContentsWrapper** offscreen_tab,
+                         const TabContents* current_tab_contents,
+                         std::string* error_message) {
+  std::vector<TabContents*> offscreen_tab_contents_vector =
+      (*offscreen_tabs_map)[ExtensionTabUtil::GetTabId(current_tab_contents)];
+
+  for (std::vector<TabContents*>::iterator
+       it_offscreen_tab_contents = offscreen_tab_contents_vector.begin();
+       it_offscreen_tab_contents != offscreen_tab_contents_vector.end();
+       ++it_offscreen_tab_contents)
+    if (ExtensionTabUtil::GetTabId(*it_offscreen_tab_contents) == tab_id) {
+      *offscreen_tab = TabContentsWrapper::GetCurrentWrapperForContents(
+          *it_offscreen_tab_contents);
+
+      return true;
+    }
+
+  *error_message = ExtensionErrorUtils::FormatErrorMessage(
+      keys::kOffscreenTabNotFoundError, base::IntToString(tab_id));
+
+  return false;
+}
+
+bool GetTabById(const int tab_id,
+                Browser* browser,
+                TabContents** tab_contents,
+                std::string* error_message) {
+  TabStripModel* tab_strip = browser->tabstrip_model();
+  for (int i = 0; i <tab_strip->count(); ++i) {
+    *tab_contents = tab_strip->GetTabContentsAt(i)->tab_contents();
+
+    if (ExtensionTabUtil::GetTabId(*tab_contents) == tab_id)
+      return true;
+  }
+
+  *error_message = ExtensionErrorUtils::FormatErrorMessage(
+      keys::kTabNotFoundError, base::IntToString(tab_id));
+
+  return false;
+}
+
+std::string GetTabUrl(const TabContents* tab_contents) {
+  return tab_contents->GetURL().spec();
+}
+
+int GetTabWidth(const TabContents* tab_contents) {
+  const TabContentsWrapper* tab =
+      TabContentsWrapper::GetCurrentWrapperForContents(tab_contents);
+
+  return tab ? tab->view()->GetContainerSize().width() : -1;
+}
+
+int GetTabHeight(const TabContents* tab_contents) {
+  const TabContentsWrapper* tab =
+      TabContentsWrapper::GetCurrentWrapperForContents(tab_contents);
+
+  return tab ? tab->view()->GetContainerSize().height() : -1;
+}
+
+void CloseOffscreenTab(TabContents* tab_contents) {
+  // TODO(alexbost): Is this the best way to close an offscreen tab?
+  delete TabContentsWrapper::GetCurrentWrapperForContents(tab_contents);
+}
+
+DictionaryValue* CreateOffscreenTabValue(const TabContentsWrapper* tab) {
+  DictionaryValue* result = new DictionaryValue();
+  result->SetInteger(keys::kIdKey,
+                     ExtensionTabUtil::GetTabId(tab->tab_contents()));
+  result->SetString(keys::kUrlKey, GetTabUrl(tab->tab_contents()));
+  result->SetInteger(keys::kWidthKey, GetTabWidth(tab->tab_contents()));
+  result->SetInteger(keys::kHeightKey, GetTabHeight(tab->tab_contents()));
+
+  return result;
+}
+
+}  // namespace
+
+// Event Manager ---------------------------------------------------------------
+
+void OffscreenTabsEventManager::RegisterForTabNotifications(
+    const TabContents* tab_contents) {
+  registrar_.Add(this,
+                 content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+                 Source<NavigationController>(&tab_contents->controller()));
+
+  registrar_.Add(this,
+                 content::NOTIFICATION_TAB_CONTENTS_DESTROYED,
+                 Source<TabContents>(tab_contents));
+}
+
+void OffscreenTabsEventManager::UnregisterForTabNotifications(
+    const TabContents* tab_contents) {
+  registrar_.Remove(this,
+                    content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+                    Source<NavigationController>(&tab_contents->controller()));
+
+  registrar_.Remove(this,
+                    content::NOTIFICATION_TAB_CONTENTS_DESTROYED,
+                    Source<TabContents>(tab_contents));
+}
+
+void OffscreenTabsEventManager::Observe(const int type,
+                                        const NotificationSource& source,
+                                        const NotificationDetails& details) {
+  TabContents* tab_contents;
+
+  if (type == content::NOTIFICATION_TAB_CONTENTS_DESTROYED)
+    tab_contents = Source<TabContents>(source).ptr();
+  else if (type == content::NOTIFICATION_NAV_ENTRY_COMMITTED)
+    tab_contents = Source<NavigationController>(source).ptr()->tab_contents();
+  else
+    return;
+

[Ken Russell (switch to Gerrit), 2011/08/23 22:46:53]

DCHECK(tab_contents)?

[alexbost, 2011/08/24 20:06:21]

Done.

+  // Close all offscreen tabs spawned by this tab
+  std::vector<TabContents*> offscreen_tab_contents_vector =
+      (*offscreen_tabs_map)[ExtensionTabUtil::GetTabId(tab_contents)];
+  for (std::vector<TabContents*>::iterator
+       it_offscreen_tab_contents = offscreen_tab_contents_vector.begin();
+       it_offscreen_tab_contents != offscreen_tab_contents_vector.end();
+       ++it_offscreen_tab_contents)
+    CloseOffscreenTab(*it_offscreen_tab_contents);
+
+  offscreen_tabs_map->erase(ExtensionTabUtil::GetTabId(tab_contents));
+
+  event_manager->UnregisterForTabNotifications(tab_contents);
+}
+
+// create ----------------------------------------------------------------------
+
+bool CreateOffscreenTabFunction::RunImpl() {
+  Browser* browser = GetCurrentBrowser();
+  if (!browser) {
+    error_ = keys::kNoCurrentWindowError;
+    return false;

[Ken Russell (switch to Gerrit), 2011/08/23 22:46:53]

Do you need to SendResponse(false) here, and elsewhere in this function where
false is returned?

[alexbost, 2011/08/24 20:06:21]

Looking at extension_tabs_module.cc, they do not call SendResponse(false) in
RunImpl() methods.

+  }
+
+  DictionaryValue* create_props;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(0, &create_props));
+
+  // Url
+  std::string url_string;
+  GURL url;
+  EXTENSION_FUNCTION_VALIDATE(
+      create_props->GetString(keys::kUrlKey, &url_string));
+  url = ResolvePossiblyRelativeURL(url_string, GetExtension());
+  if (!url.is_valid()) {
+    error_ = ExtensionErrorUtils::FormatErrorMessage(
+        keys::kInvalidUrlError, url_string);
+    return false;
+  }
+  if (IsCrashURL(url)) {
+    error_ = keys::kNoCrashBrowserError;
+    return false;
+  }
+
+  // Width and height
+  gfx::Rect window_bounds;
+  bool maximized;
+  if (!create_props->HasKey(keys::kWidthKey) ||
+      !create_props->HasKey(keys::kHeightKey))
+    WindowSizer::GetBrowserWindowBounds(std::string(), gfx::Rect(),
+                                        browser, &window_bounds,
+                                        &maximized);
+
+  int width;
+  if (create_props->HasKey(keys::kWidthKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        create_props->GetInteger(keys::kWidthKey, &width));
+  else
+    width = window_bounds.width();
+
+  int height;
+  if (create_props->HasKey(keys::kHeightKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        create_props->GetInteger(keys::kHeightKey, &height));
+  else
+    height = window_bounds.height();
+
+  // New offscreen tab
+  TabContents* offscreen_tab_contents =
+      new TabContents(profile_, NULL, MSG_ROUTING_NONE, NULL, NULL);
+  TabContentsWrapper* offscreen_tab =
+      new TabContentsWrapper(offscreen_tab_contents);
+
+  // Setting the size starts the renderer
+  offscreen_tab_contents->view()->SizeContents(*new gfx::Size(width, height));

[Ken Russell (switch to Gerrit), 2011/08/23 22:46:53]

This is a memory leak. Just use: ->SizeContents(gfx::Size(width, height));

[alexbost, 2011/08/24 20:06:21]

Done.

+
+  // Navigate
+  offscreen_tab_contents->controller().LoadURL(
+      url, GURL(), PageTransition::LINK);
+
+  // Map the offscreen tab to the tab that spawned it
+  TabContents* tab_contents =
+      dispatcher()->delegate()->GetAssociatedTabContents();
+
+  (*offscreen_tabs_map)[ExtensionTabUtil::GetTabId(tab_contents)].
+      push_back(offscreen_tab_contents);
+
+  // Register for tab notifications
+  // if this is the first offscreen tab spawned by the tab
+  if ((*offscreen_tabs_map)[ExtensionTabUtil::GetTabId(tab_contents)].
+      size() == 1) {
+    if (!event_manager)
+      event_manager = new OffscreenTabsEventManager();
+
+    event_manager->RegisterForTabNotifications(tab_contents);
+  }
+
+  // Callback
+  if (has_callback()) {
+    result_.reset(CreateOffscreenTabValue(offscreen_tab));
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// get -------------------------------------------------------------------------
+
+bool GetOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+  TabContentsWrapper* tab = NULL;
+  TabContents* current_tab_contents =
+      dispatcher()->delegate()->GetAssociatedTabContents();
+  if (!GetOffscreenTabById(tab_id, &tab, current_tab_contents, &error_))
+    return false;

[Ken Russell (switch to Gerrit), 2011/08/23 22:46:53]

Is a SendReponse(false) needed here? If so, also elsewhere in this file where
functions end with SendResponse(true) but can abort early. Also would be ideal
to test some of the failure cases in a unit test -- for example, by passing an
obviously invalid offscreen tab ID to this function. (Actually, I see now that
you do have a negative test for this API, which is good.)

[alexbost, 2011/08/24 20:06:21]

See above.

+
+  result_.reset(CreateOffscreenTabValue(tab));
+  SendResponse(true);
+
+  return true;
+}
+
+// getAll ----------------------------------------------------------------------
+
+bool GetAllOffscreenTabFunction::RunImpl() {
+  TabContents* current_tab_contents =
+      dispatcher()->delegate()->GetAssociatedTabContents();
+
+  std::vector<TabContents*> offscreen_tab_contents_vector =
+    (*offscreen_tabs_map)[ExtensionTabUtil::GetTabId(current_tab_contents)];
+
+  ListValue* tab_list = new ListValue();
+
+  for (std::vector<TabContents*>::iterator
+       it_offscreen_tab_contents = offscreen_tab_contents_vector.begin();
+       it_offscreen_tab_contents != offscreen_tab_contents_vector.end();
+       ++it_offscreen_tab_contents)
+    tab_list->Append(CreateOffscreenTabValue(TabContentsWrapper::
+        GetCurrentWrapperForContents(*it_offscreen_tab_contents)));
+
+  result_.reset(tab_list);
+  SendResponse(true);
+
+  return true;
+}
+
+// remove ----------------------------------------------------------------------
+
+bool RemoveOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+
+  for (OffscreenTabsMap::iterator it = offscreen_tabs_map->begin();
+       it != offscreen_tabs_map->end(); ++it)
+    for (std::vector<TabContents*>::iterator it_offscreen_tab_contents =
+         it->second.begin();
+         it_offscreen_tab_contents != it->second.end();
+         ++it_offscreen_tab_contents)
+      if (ExtensionTabUtil::GetTabId(*it_offscreen_tab_contents) == tab_id) {
+        TabContents* tab_contents;
+        if (!GetTabById(
+            it->first, GetCurrentBrowser(), &tab_contents, &error_))
+          return false;
+
+        CloseOffscreenTab(*it_offscreen_tab_contents);
+
+        it->second.erase(it_offscreen_tab_contents);
+
+        // If this was the last offscreen tab for the tab,
+        // unregister the tab for notifications and remove it from the map
+        if (it->second.empty()) {
+          event_manager->UnregisterForTabNotifications(tab_contents);
+          offscreen_tabs_map->erase(it);
+        }
+
+        return true;
+      }
+
+  error_ = ExtensionErrorUtils::FormatErrorMessage(
+      keys::kOffscreenTabNotFoundError, base::IntToString(tab_id));
+  return false;
+}
+
+// sendKeyboardEvent -----------------------------------------------------------
+
+bool SendKeyboardEventOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+  TabContentsWrapper* tab = NULL;
+  TabContents* current_tab_contents =
+      dispatcher()->delegate()->GetAssociatedTabContents();
+  if (!GetOffscreenTabById(tab_id, &tab, current_tab_contents, &error_))
+    return false;

[Ken Russell (switch to Gerrit), 2011/08/23 22:46:53]

Here and below, is any SendResponse(false) needed?

[alexbost, 2011/08/24 20:06:21]

See above.

+
+  // JavaScript KeyboardEvent
+  DictionaryValue* dict;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &dict));
+
+  NativeWebKeyboardEvent keyboard_event;
+
+  // Type
+  std::string type;
+  if (dict->HasKey(keys::kKeyboardEventTypeKey)) {
+    EXTENSION_FUNCTION_VALIDATE(
+        dict->GetString(keys::kKeyboardEventTypeKey, &type));
+  } else {
+    error_ = keys::kInvalidKeyboardEventObjectError;
+    return false;
+  }
+
+  if (type.compare(keys::kKeyboardEventTypeValueKeypress) == 0) {
+    keyboard_event.type = WebInputEvent::Char;
+  } else if (type.compare(keys::kKeyboardEventTypeValueKeydown) == 0) {
+    keyboard_event.type = WebInputEvent::KeyDown;
+  } else if (type.compare(keys::kKeyboardEventTypeValueKeyup) == 0) {
+    keyboard_event.type = WebInputEvent::KeyUp;
+  } else {
+    error_ = keys::kInvalidKeyboardEventObjectError;
+    return false;
+  }
+
+  // Key code
+  int key_code;
+  if (dict->HasKey(keys::kKeyboardEventKeyCodeKey)) {
+    EXTENSION_FUNCTION_VALIDATE(
+        dict->GetInteger(keys::kKeyboardEventKeyCodeKey, &key_code));
+  } else {
+    error_ = keys::kInvalidKeyboardEventObjectError;
+    return false;
+  }
+
+  keyboard_event.nativeKeyCode = key_code;
+  keyboard_event.windowsKeyCode = key_code;
+
+  // Key identifier
+  keyboard_event.setKeyIdentifierFromWindowsKeyCode();
+
+  // Keypress = type character
+  if (type.compare(keys::kKeyboardEventTypeValueKeypress) == 0) {
+    int char_code;
+    if (dict->HasKey(keys::kKeyboardEventCharCodeKey)) {
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetInteger(keys::kKeyboardEventCharCodeKey, &char_code));
+      keyboard_event.text[0] = char_code;
+      keyboard_event.unmodifiedText[0] = char_code;
+    } else {
+      error_ = keys::kInvalidKeyboardEventObjectError;
+      return false;
+    }
+  }
+
+  // Modifiers
+  bool alt_key;
+  if (dict->HasKey(keys::kKeyboardEventAltKeyKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        dict->GetBoolean(keys::kKeyboardEventAltKeyKey, &alt_key));
+  if (alt_key)
+    keyboard_event.modifiers |= WebInputEvent::AltKey;
+
+  bool ctrl_key;
+  if (dict->HasKey(keys::kKeyboardEventCtrlKeyKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        dict->GetBoolean(keys::kKeyboardEventCtrlKeyKey, &ctrl_key));
+  if (ctrl_key)
+    keyboard_event.modifiers |= WebInputEvent::ControlKey;
+
+  bool meta_key = false;
+  if (dict->HasKey(keys::kMouseEventMetaKeyKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        dict->GetBoolean(keys::kMouseEventMetaKeyKey, &meta_key));
+  if (meta_key)
+    keyboard_event.modifiers |= WebInputEvent::MetaKey;
+
+  bool shift_key;
+  if (dict->HasKey(keys::kKeyboardEventShiftKeyKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        dict->GetBoolean(keys::kKeyboardEventShiftKeyKey, &shift_key));
+  if (shift_key)
+    keyboard_event.modifiers |= WebInputEvent::ShiftKey;
+
+  // Forward event
+  tab->tab_contents()->render_view_host()->
+      ForwardKeyboardEvent(keyboard_event);
+
+  // Callback
+  if (has_callback()) {
+    result_.reset(CreateOffscreenTabValue(tab));
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// sendMouseEvent --------------------------------------------------------------
+
+bool SendMouseEventOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+  TabContentsWrapper* tab = NULL;
+  TabContents* current_tab_contents =
+      dispatcher()->delegate()->GetAssociatedTabContents();
+  if (!GetOffscreenTabById(tab_id, &tab, current_tab_contents, &error_))
+    return false;
+
+  // JavaScript MouseEvent
+  DictionaryValue* dict;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &dict));
+
+  std::string type;
+  if (dict->HasKey(keys::kMouseEventTypeKey)) {
+    EXTENSION_FUNCTION_VALIDATE(
+        dict->GetString(keys::kMouseEventTypeKey, &type));
+  } else {
+    error_ = keys::kInvalidMouseEventObjectError;
+    return false;
+  }
+
+  if (type.compare(keys::kMouseEventTypeValueMousewheel) == 0) {
+    WebKit::WebMouseWheelEvent wheel_event;
+
+    // Type
+    wheel_event.type = WebInputEvent::MouseWheel;
+
+    // deltaX, deltaY
+    if (dict->HasKey(keys::kMouseEventWheelDeltaXKey) &&
+        dict->HasKey(keys::kMouseEventWheelDeltaYKey)) {
+      int delta_x, delta_y;
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetInteger(keys::kMouseEventWheelDeltaXKey, &delta_x));
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetInteger(keys::kMouseEventWheelDeltaYKey, &delta_y));
+      wheel_event.deltaX = delta_x;
+      wheel_event.deltaY = delta_y;
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    // Forward the event
+    tab->tab_contents()->render_view_host()->ForwardWheelEvent(wheel_event);
+  } else {
+    WebKit::WebMouseEvent mouse_event;
+
+    // Type
+    if (type.compare(keys::kMouseEventTypeValueMousedown) == 0 ||
+        type.compare(keys::kMouseEventTypeValueClick) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseDown;
+    } else if (type.compare(keys::kMouseEventTypeValueMouseup) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseUp;
+    } else if (type.compare(keys::kMouseEventTypeValueMousemove) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseMove;
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    // Button
+    int button;
+    if (dict->HasKey(keys::kMouseEventButtonKey)) {
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetInteger(keys::kMouseEventButtonKey, &button));
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    if (button == keys::kMouseEventButtonValueLeft) {
+      mouse_event.button = WebKit::WebMouseEvent::ButtonLeft;
+    } else if (button == keys::kMouseEventButtonValueMiddle) {
+      mouse_event.button = WebKit::WebMouseEvent::ButtonMiddle;
+    } else if (button == keys::kMouseEventButtonValueRight) {
+      mouse_event.button = WebKit::WebMouseEvent::ButtonRight;
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    // x, y
+    if (HasOptionalArgument(2) && HasOptionalArgument(3)) {
+      EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(2, &mouse_event.x));
+      EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(3, &mouse_event.y));
+    } else {
+      error_ = keys::kNoMouseCoordinatesError;
+      return false;
+    }
+
+    // Modifiers
+    bool alt_key = false;
+    if (dict->HasKey(keys::kMouseEventAltKeyKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetBoolean(keys::kMouseEventAltKeyKey, &alt_key));
+    if (alt_key)
+      mouse_event.modifiers |= WebInputEvent::AltKey;
+
+    bool ctrl_key = false;
+    if (dict->HasKey(keys::kMouseEventCtrlKeyKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetBoolean(keys::kMouseEventCtrlKeyKey, &ctrl_key));
+    if (ctrl_key)
+      mouse_event.modifiers |= WebInputEvent::ControlKey;
+
+    bool meta_key = false;
+    if (dict->HasKey(keys::kMouseEventMetaKeyKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetBoolean(keys::kMouseEventMetaKeyKey, &meta_key));
+    if (meta_key)
+      mouse_event.modifiers |= WebInputEvent::MetaKey;
+
+    bool shift_key = false;
+    if (dict->HasKey(keys::kMouseEventShiftKeyKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          dict->GetBoolean(keys::kMouseEventShiftKeyKey, &shift_key));
+    if (shift_key)
+      mouse_event.modifiers |= WebInputEvent::ShiftKey;
+
+    // Click count
+    mouse_event.clickCount = 1;
+
+    // Forward the event
+    tab->tab_contents()->render_view_host()->ForwardMouseEvent(mouse_event);
+
+    // If the event is a click,
+    // fire a mouseup event in addition to the mousedown
+    if (type.compare(keys::kMouseEventTypeValueClick) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseUp;
+      tab->tab_contents()->render_view_host()->ForwardMouseEvent(mouse_event);
+    }
+  }
+
+  // Callback
+  if (has_callback()) {
+    result_.reset(CreateOffscreenTabValue(tab));
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// toDataUrl -------------------------------------------------------------------
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+// TODO(alexbost): We want to optimize this function in order to get more image
+// updates on the browser side. One improvement would be to implement another
+// hash map to get offscreen tabs in O(1).
+bool ToDataUrlOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+  TabContentsWrapper* tab = NULL;
+  TabContents* current_tab_contents =
+      dispatcher()->delegate()->GetAssociatedTabContents();
+  if (!GetOffscreenTabById(tab_id, &tab, current_tab_contents, &error_))
+    return false;
+
+  image_format_ = FORMAT_JPEG;  // Default format is JPEG.
+  image_quality_ = kDefaultQuality;  // Default quality setting.
+
+  if (HasOptionalArgument(1)) {
+    DictionaryValue* options;
+    EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &options));
+
+    if (options->HasKey(keys::kFormatKey)) {
+      std::string format;
+      EXTENSION_FUNCTION_VALIDATE(
+          options->GetString(keys::kFormatKey, &format));
+
+      if (format == keys::kFormatValueJpeg) {
+        image_format_ = FORMAT_JPEG;
+      } else if (format == keys::kFormatValuePng) {
+        image_format_ = FORMAT_PNG;
+      } else {
+        // Schema validation should make this unreachable.
+        EXTENSION_FUNCTION_VALIDATE(0);
+      }
+    }
+
+    if (options->HasKey(keys::kQualityKey)) {
+      EXTENSION_FUNCTION_VALIDATE(
+          options->GetInteger(keys::kQualityKey, &image_quality_));
+    }
+  }
+
+  // captureVisibleTab() can return an image containing sensitive information
+  // that the browser would otherwise protect.  Ensure the extension has
+  // permission to do this.
+  if (!GetExtension()->
+      CanCaptureVisiblePage(tab->tab_contents()->GetURL(), &error_))
+    return false;
+
+// The backing store approach does not work on Mac
+// TODO(alexbost): Test on Windows
+#if !defined(OS_MACOSX)
+  RenderViewHost* render_view_host = tab->tab_contents()->render_view_host();
+
+  // If a backing store is cached for the tab we want to capture,
+  // and it can be copied into a bitmap, then use it to generate the image.
+  BackingStore* backing_store = render_view_host->GetBackingStore(false);
+  if (backing_store && CaptureSnapshotFromBackingStore(backing_store))
+    return true;
+#endif
+
+  // Ask the renderer for a snapshot of the tab.
+  tab->CaptureSnapshot();
+  registrar_.Add(this,
+               chrome::NOTIFICATION_TAB_SNAPSHOT_TAKEN,
+               Source<TabContentsWrapper>(tab));
+
+  AddRef();  // Balanced in ToDataUrlOffscreenTabFunction::Observe().
+
+  return true;
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+// Build the image of a tab's contents out of a backing store.
+// This may fail if we can not copy a backing store into a bitmap.
+// For example, some uncommon X11 visual modes are not supported by
+// CopyFromBackingStore().
+bool ToDataUrlOffscreenTabFunction::CaptureSnapshotFromBackingStore(
+    BackingStore* backing_store) {
+
+  skia::PlatformCanvas temp_canvas;
+  if (!backing_store->CopyFromBackingStore(gfx::Rect(backing_store->size()),
+                                           &temp_canvas)) {
+    return false;
+  }
+  VLOG(1) << "captureVisibleTab() got image from backing store.";
+
+  SendResultFromBitmap(
+      skia::GetTopDevice(temp_canvas)->accessBitmap(false));
+  return true;
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+void ToDataUrlOffscreenTabFunction::Observe(const int type,
+                                            const NotificationSource& source,
+                                           const NotificationDetails& details) {
+  DCHECK(type == chrome::NOTIFICATION_TAB_SNAPSHOT_TAKEN);
+
+  const SkBitmap *screen_capture = Details<const SkBitmap>(details).ptr();
+  const bool error = screen_capture->empty();
+
+  if (error) {
+    error_ = keys::kInternalVisibleTabCaptureError;
+    SendResponse(false);
+  } else {
+    VLOG(1) << "Got image from renderer.";
+    SendResultFromBitmap(*screen_capture);
+  }
+
+  Release();  // Balanced in ToDataUrlOffscreenTabFunction::RunImpl().
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+// Turn a bitmap of the screen into an image, set that image as the result,
+// and call SendResponse().
+void ToDataUrlOffscreenTabFunction::SendResultFromBitmap(
+    const SkBitmap& screen_capture) {
+  std::vector<unsigned char> data;
+  SkAutoLockPixels screen_capture_lock(screen_capture);
+  bool encoded = false;
+  std::string mime_type;
+  switch (image_format_) {
+    case FORMAT_JPEG:
+      encoded = gfx::JPEGCodec::Encode(
+          reinterpret_cast<unsigned char*>(screen_capture.getAddr32(0, 0)),
+          gfx::JPEGCodec::FORMAT_SkBitmap,
+          screen_capture.width(),
+          screen_capture.height(),
+          static_cast<int>(screen_capture.rowBytes()),
+          image_quality_,
+          &data);
+      mime_type = keys::kMimeTypeJpeg;
+      break;
+    case FORMAT_PNG:
+      encoded = gfx::PNGCodec::EncodeBGRASkBitmap(
+          screen_capture,
+          true,  // Discard transparency.
+          &data);
+      mime_type = keys::kMimeTypePng;
+      break;
+    default:
+      NOTREACHED() << "Invalid image format.";
+  }
+
+  if (!encoded) {
+    error_ = keys::kInternalVisibleTabCaptureError;
+    SendResponse(false);
+    return;
+  }
+
+  std::string base64_result;
+  base::StringPiece stream_as_string(
+      reinterpret_cast<const char*>(vector_as_array(&data)), data.size());
+
+  base::Base64Encode(stream_as_string, &base64_result);
+  base64_result.insert(0, base::StringPrintf("data:%s;base64,",
+                                             mime_type.c_str()));
+  result_.reset(new StringValue(base64_result));
+  SendResponse(true);
+}
+
+// update ----------------------------------------------------------------------
+
+UpdateOffscreenTabFunction::UpdateOffscreenTabFunction() {
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+bool UpdateOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+  TabContentsWrapper* tab = NULL;
+  TabContents* current_tab_contents =
+      dispatcher()->delegate()->GetAssociatedTabContents();
+  if (!GetOffscreenTabById(tab_id, &tab, current_tab_contents, &error_))
+    return false;
+
+  DictionaryValue* update_props;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &update_props));
+
+  // Url
+  if (update_props->HasKey(keys::kUrlKey)) {
+    std::string url_string;
+    GURL url;
+    EXTENSION_FUNCTION_VALIDATE(
+        update_props->GetString(keys::kUrlKey, &url_string));
+    url = ResolvePossiblyRelativeURL(url_string, GetExtension());
+    if (!url.is_valid()) {
+      error_ = ExtensionErrorUtils::FormatErrorMessage(
+          keys::kInvalidUrlError, url_string);
+      return false;
+    }
+    if (IsCrashURL(url)) {
+      error_ = keys::kNoCrashBrowserError;
+      return false;
+    }
+
+    // JavaScript URLs can do the same kinds of things as cross-origin XHR, so
+    // we need to check host permissions before allowing them.
+    if (url.SchemeIs(chrome::kJavaScriptScheme)) {
+      if (!GetExtension()->CanExecuteScriptOnPage(
+              tab->tab_contents()->GetURL(), NULL, &error_)) {
+        return false;
+      }
+
+      ExtensionMsg_ExecuteCode_Params params;
+      params.request_id = request_id();
+      params.extension_id = extension_id();
+      params.is_javascript = true;
+      params.code = url.path();
+      params.all_frames = false;
+      params.in_main_world = true;
+
+      RenderViewHost* render_view_host =
+          tab->tab_contents()->render_view_host();
+      render_view_host->Send(
+          new ExtensionMsg_ExecuteCode(render_view_host->routing_id(),
+                                       params));
+
+      Observe(tab->tab_contents());
+      AddRef();  // balanced in Observe()
+
+      return true;
+    }
+
+    tab->tab_contents()->controller().
+        LoadURL(url, GURL(), PageTransition::LINK);
+
+    // The URL of a tab contents never actually changes to a JavaScript URL, so
+    // this check only makes sense in other cases.
+    if (!url.SchemeIs(chrome::kJavaScriptScheme))
+      DCHECK_EQ(url.spec(), tab->tab_contents()->GetURL().spec());
+  }
+
+  // Width and height
+  if (update_props->HasKey(keys::kWidthKey) ||
+      update_props->HasKey(keys::kHeightKey)) {
+    int width;
+    if (update_props->HasKey(keys::kWidthKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          update_props->GetInteger(keys::kWidthKey, &width));
+    else
+      GetTabWidth(tab->tab_contents());
+
+    int height;
+    if (update_props->HasKey(keys::kHeightKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          update_props->GetInteger(keys::kHeightKey, &height));
+    else
+      GetTabHeight(tab->tab_contents());
+
+    tab->tab_contents()->view()->SizeContents(*new gfx::Size(width, height));
+  }
+
+  // Callback
+  if (has_callback()) {
+    result_.reset(CreateOffscreenTabValue(tab));
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+bool UpdateOffscreenTabFunction::OnMessageReceived(
+    const IPC::Message& message) {
+  if (message.type() != ExtensionHostMsg_ExecuteCodeFinished::ID)
+    return false;
+
+  int message_request_id;
+  void* iter = NULL;
+  if (!message.ReadInt(&iter, &message_request_id)) {
+    NOTREACHED() << "malformed extension message";
+    return true;
+  }
+
+  if (message_request_id != request_id())
+    return false;
+
+  IPC_BEGIN_MESSAGE_MAP(UpdateOffscreenTabFunction, message)
+    IPC_MESSAGE_HANDLER(ExtensionHostMsg_ExecuteCodeFinished,
+                        OnExecuteCodeFinished)
+  IPC_END_MESSAGE_MAP()
+  return true;
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+void UpdateOffscreenTabFunction::OnExecuteCodeFinished(int request_id,
+                                              bool success,
+                                              const std::string& error) {
+  if (!error.empty()) {
+    CHECK(!success);
+    error_ = error;
+  }
+
+  SendResponse(success);
+
+  Observe(NULL);
+  Release();  // balanced in Execute()
+}
+
+