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/json/json_writer.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/values.h"
+#include "chrome/browser/extensions/extension_event_router.h"
+#include "chrome/browser/extensions/extension_function_dispatcher.h"
+#include "chrome/browser/extensions/extension_host.h"
+#include "chrome/browser/extensions/extension_message_service.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/ui/browser.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/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/content_client.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;
+
+namespace {
+
+// Offscreen Tab ---------------------------------------------------------------
+
+// This class is responsible for the creation and destruction of offscreen tabs,
+// as well as dispatching an onUpdated event.
+class OffscreenTab : public NotificationObserver {
+ public:
+  OffscreenTab();
+  ~OffscreenTab();

[sky, 2011/09/14 23:34:44]

virtual

[alexbost, 2011/09/15 03:29:49]

Done.

+  void Init(const GURL& url,
+            const int width,
+            const int height,
+            const Extension* extension,
+            Profile* profile,
+            ExtensionFunctionDispatcher* dispatcher);
+
+  inline TabContents* contents();

[sky, 2011/09/14 23:34:44]

Sorry, I didn't mean use the inline keyword, instead inline the implementation,
eg:

TabContents* contents()  { return tab_.get(); }

But note that the name should match the variable name. So, either rename to tab
or rename tab_ to contents_.

[alexbost, 2011/09/15 03:29:49]

I would like to have a method in this class to return TabContents instead of
TabContentsWrapper since TabContents are needed to call various methods
throughout the code. So maybe I should change the name back to GetContents()?
This applies to the Tab class as well.

[sky, 2011/09/15 20:05:57]

The names only need match if you're returning a field. If you're not returning a
field, you can use something else. Maybe:

TabContents* contents() { return tab_->tab_contents(); }

[alexbost, 2011/09/15 20:57:57]

Done.

+  DictionaryValue* CreateValue();  // Creates an appropriate offscreen tab

[sky, 2011/09/14 23:34:44]

Document caller owns return value.

[alexbost, 2011/09/15 03:29:49]

Done.

+                                   // object returned by the API.
+
+  void SetUrl(const GURL& url);
+  void SetSize(int width, int height);
+
+ private:
+  virtual void Observe(const int type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
+  NotificationRegistrar registrar_;
+
+  scoped_ptr<TabContentsWrapper> tab_;  // TabContentsWrapper associated with
+                                        // this offscreen tab.
+
+  DISALLOW_COPY_AND_ASSIGN(OffscreenTab);
+};
+
+typedef std::vector<OffscreenTab*> TabVector;
+typedef TabVector::iterator TabIterator;
+
+// Tab -------------------------------------------------------------------------
+
+// This class holds info about a tab that has spawned at least one offscreen tab

[sky, 2011/09/14 23:34:44]

'tab' -> 'tab.'

[alexbost, 2011/09/15 03:29:49]

Done.

+// We will call such tab the 'parent' of the offscreen tabs it has spawned.
+// Each Tab keeps track of its child offscreen tabs. The Tab is also responsible
+// for killing its children when it navigates away or gets closed.
+class Tab : public NotificationObserver {
+ public:
+  Tab();
+  ~Tab();

[sky, 2011/09/14 23:34:44]

virtual

[alexbost, 2011/09/15 03:29:49]

Done.

+  void Init(TabContents* tab_contents, const std::string& extension_id);
+
+  inline TabContents* contents();
+  inline TabVector* offscreen_tabs();

[sky, 2011/09/14 23:34:44]

const TabVector&

[alexbost, 2011/09/15 03:29:49]

Done.

+  const std::string& GetExtensionId() const;
+
+  void AddOffscreenTab(OffscreenTab *tab);

[sky, 2011/09/14 23:34:44]

Document ownership for these two.

[alexbost, 2011/09/15 03:29:49]

Done.

+  void RemoveOffscreenTab(OffscreenTab *tab);
+
+ private:
+  virtual void Observe(const int type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
+  NotificationRegistrar registrar_;
+
+  TabContentsWrapper* tab_;  // TabContentsWrapper associated with this tab.

[sky, 2011/09/14 23:34:44]

Your description says 'We will call such tab the 'parent'', so I would assume
this variable is named parent too.

[alexbost, 2011/09/15 03:29:49]

Done.

+  TabVector offscreen_tabs_;  // Offscreen tabs spawned by this tab.
+  std::string extension_id_;  // Id of the extension running in this tab.
+
+  DISALLOW_COPY_AND_ASSIGN(Tab);
+};
+
+// Map -------------------------------------------------------------------------
+
+// This map keeps track of all tabs that are happy parents of offscreen tabs.
+class Map {
+ public:
+  Map();
+  ~Map();
+
+  // Gets an offscreen tab by ID.
+  bool GetOffscreenTab(const int tab_id,
+                       ExtensionFunctionDispatcher* dispatcher,
+                       Profile* profile,
+                       OffscreenTab** offscreen_tab,
+                       std::string* error_message);
+  // Gets a parent tab by ID.
+  bool GetTab(const int tab_id,
+              Tab** tab,
+              std::string* error_message);
+  // Gets the parent tab of an offscreen tab.
+  bool GetTabOfOffscreenTab(TabContents* offscreen_tab_contents,
+                            Tab** tab,
+                            std::string* error_message);
+  // Creates a mapping between a parent tab and an offscreen tab.
+  bool AddOffscreenTab(OffscreenTab* offscreen_tab,
+                       ExtensionFunctionDispatcher* dispatcher,
+                       Profile* profile,
+                       const std::string& ext_id,
+                       std::string* error_message);
+  // Removes the mapping between a parent tab and an offscreen tab.
+  bool RemoveOffscreenTab(const int tab_id,
+                          ExtensionFunctionDispatcher* dispatcher,
+                          Profile* profile,
+                          std::string* error_message);
+  // Removes a parent tab from the map along with its child offscreen tabs.
+  bool RemoveTab(const int tab_id, std::string* error_message);
+
+ private:
+  typedef base::hash_map<int, Tab*> TabMap;
+  TabMap map;
+
+  DISALLOW_COPY_AND_ASSIGN(Map);
+};
+
+// Variables -------------------------------------------------------------------
+
+Map* map = NULL;
+
+// We are assuming that offscreen tabs will not be created by background pages
+// with the exception of the API test background page. We keep track of the
+// offscreen tabs associated with the test API background page via this variable
+// These tab contents are created just for convenience and do not do anything.
+// TODO(alexbost): Think about handling multiple background pages each spawning
+// offscreen tabs. Would background pages want to spawn offscreen tabs?
+TabContents* background_page_tab_contents = NULL;
+
+// Util ------------------------------------------------------------------------
+
+// Gets the map of parent tabs to offscreen tabs.
+Map* GetMap() {
+  if (map == NULL)
+    map = new Map();
+
+  return map;
+}
+
+// Gets the TabContents associated with the test API background page.
+TabContents* GetBackgroundPageTabContents(Profile* profile) {
+  if (profile && background_page_tab_contents == NULL) {
+    background_page_tab_contents =
+        new TabContents(profile, NULL, MSG_ROUTING_NONE, NULL, NULL);
+    new TabContentsWrapper(background_page_tab_contents);
+  }
+
+  return background_page_tab_contents;
+}
+
+// Gets the contents of the tab that instantiated the extension API call.
+// In the case of background pages we use tab contents created by us.
+bool GetCurrentTab(ExtensionFunctionDispatcher* dispatcher,
+                   Profile* profile,
+                   TabContents** tab_contents,
+                   std::string* error_message) {
+  *tab_contents = dispatcher->delegate()->GetAssociatedTabContents();
+
+  // Background page (no associated tab contents).
+  if (!*tab_contents)
+    *tab_contents = GetBackgroundPageTabContents(profile);
+
+  if (*tab_contents)
+    return true;
+
+  *error_message = keys::kCurrentTabNotFound;
+  return false;
+}
+
+// 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));
+}
+
+// Gets the size of a tab.
+gfx::Size GetTabSize(const TabContentsWrapper* tab) {
+  return tab->view()->GetContainerSize();

[sky, 2011/09/14 23:34:44]

At this point this function isn't saving you much. How about using
tab->view()->GetContainSize() were appropriate.

[alexbost, 2011/09/15 03:29:49]

Done.

+}
+
+// Offscreen Tab ---------------------------------------------------------------
+
+OffscreenTab::OffscreenTab() {}
+OffscreenTab::~OffscreenTab() {}
+
+void OffscreenTab::Init(const GURL& url,
+                        const int width,
+                        const int height,
+                        const Extension* extension,

[sky, 2011/09/14 23:34:44]

It doesn't look like you use extension or dispatcher.

[alexbost, 2011/09/15 03:29:49]

Done.

+                        Profile* profile,
+                        ExtensionFunctionDispatcher* dispatcher) {
+  // Create the offscreen tab.
+  TabContents* tab_contents = new TabContents(
+      profile, NULL, MSG_ROUTING_NONE, NULL, NULL);
+  tab_.reset(new TabContentsWrapper(tab_contents));
+
+  SetSize(width, height);  // Setting the size starts the renderer.
+  SetUrl(url);
+
+  // Register for tab notifications.
+  registrar_.Add(this,
+                 content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+                 Source<NavigationController>(&contents()->controller()));
+}
+
+inline TabContents* OffscreenTab::contents() {
+  return tab_.get()->tab_contents();
+}
+
+DictionaryValue* OffscreenTab::CreateValue() {
+  DictionaryValue* result = new DictionaryValue();
+
+  result->SetInteger(keys::kIdKey, ExtensionTabUtil::GetTabId(contents()));
+  result->SetString(keys::kUrlKey, contents()->GetURL().spec());
+  result->SetInteger(keys::kWidthKey, GetTabSize(
+      TabContentsWrapper::GetCurrentWrapperForContents(contents())).width());
+  result->SetInteger(keys::kHeightKey, GetTabSize(
+      TabContentsWrapper::GetCurrentWrapperForContents(contents())).height());
+
+  return result;
+}
+
+void OffscreenTab::SetUrl(const GURL& url) {
+  contents()->controller().LoadURL(
+      url, GURL(), PageTransition::LINK, std::string());
+}
+
+void OffscreenTab::SetSize(int width, int height) {
+  contents()->view()->SizeContents(gfx::Size(width, height));
+}
+
+void OffscreenTab::Observe(const int type,
+                           const NotificationSource& source,
+                           const NotificationDetails& details) {
+  DCHECK_EQ(content::NOTIFICATION_NAV_ENTRY_COMMITTED, type);
+
+  DictionaryValue* changed_properties = new DictionaryValue();
+  changed_properties->SetString(keys::kUrlKey, contents()->GetURL().spec());
+
+  ListValue args;
+  args.Append(
+      Value::CreateIntegerValue(ExtensionTabUtil::GetTabId(contents())));
+  args.Append(changed_properties);
+  args.Append(CreateValue());
+  std::string json_args;
+  base::JSONWriter::Write(&args, false, &json_args);
+
+  Tab* tab;
+  DCHECK(GetMap()->GetTabOfOffscreenTab(contents(), &tab, new std::string()));

[sky, 2011/09/14 23:34:44]

DCHECKs aren't compiled in release build, which means this whole line would not
be compiled.
Instead have DCHECK(*tab) on the next line.

[alexbost, 2011/09/15 03:29:49]

Done.

+
+  ListValue event_args;
+  event_args.Set(0, Value::CreateStringValue(keys::kEventOnUpdated));
+  event_args.Set(1, Value::CreateStringValue(json_args));
+
+  // Dispatch an onUpdated event.
+
+  // The primary use case for broadcasting the event is
+  // when the offscreen tab is generated by a test API background page.
+  if (tab->contents() == GetBackgroundPageTabContents(NULL)) {
+    Profile* profile = Profile::FromBrowserContext(

[sky, 2011/09/14 23:34:44]

Get the profile from tab->tab_->profile().

[alexbost, 2011/09/15 03:29:49]

Done.

+        contents()->browser_context());
+    profile->GetExtensionEventRouter()->DispatchEventToRenderers(
+        keys::kEventOnUpdated, json_args, profile, GURL());
+  // Send a routed event directly to the parent tab.

[sky, 2011/09/14 23:34:44]

Move to line 341, and indent.

[alexbost, 2011/09/15 03:29:49]

Done.

+  } else {
+    tab->contents()->render_view_host()->process()->Send(
+        new ExtensionMsg_MessageInvoke(
+            tab->contents()->render_view_host()->routing_id(),
+            tab->GetExtensionId(),
+            keys::kDispatchEvent,
+            event_args,
+            GURL()));
+  }
+}
+
+// Tab -------------------------------------------------------------------------
+
+Tab::Tab() {}

[sky, 2011/09/14 23:34:44]

initialize tab_

[alexbost, 2011/09/15 03:29:49]

Done.

+Tab::~Tab() {
+  // Kill child offscreen tabs.
+  STLDeleteElements(&offscreen_tabs_);
+
+  DCHECK(GetMap()->RemoveTab(

[sky, 2011/09/14 23:34:44]

assign to a boolean, then DCHECK(removed).

[alexbost, 2011/09/15 03:29:49]

Done.

+      ExtensionTabUtil::GetTabId(contents()), new std::string()));
+}
+
+void Tab::Init(TabContents* tab_contents, const std::string& extension_id) {
+  tab_ = TabContentsWrapper::GetCurrentWrapperForContents(tab_contents);

[sky, 2011/09/14 23:34:44]

How do you know there is TabContentsWrapper associated with tab_contents? Might
a background page use this api?

[alexbost, 2011/09/15 03:29:49]

I create an artificial TabContentsWrapper in GetBackgroundPageTabContents. We
are assuming the only background page that will use the API is the API test's
one.

[sky, 2011/09/15 20:05:57]

By background page I meant one of these:
http://code.google.com/chrome/extensions/background_pages.html . I'm not sure if
such background pages always have a TabContentsWrapper associated with them.

[alexbost, 2011/09/15 20:57:57]

I think we are talking about the same background page concept. I create a
TabContentsWrapper in GetBackgroundPageTabContents (line 199).

[sky, 2011/09/15 21:41:36]

If you're saying that all background pages are routed through you're new API,
than that's fine. But if the existing extensions API is creating a background
TabContents some where else that doesn't have a TabContentsWrapper associated
with it, there would be problems.

[alexbost, 2011/09/15 23:01:29]

If a background page ends up calling this method, then we will already have
created not only a fake TabContentsWrapper for the background page but also a
fake TabContents. See GetBackgroundPageTabContents. I've added CHECKs to verify
this logic.

+  extension_id_ = extension_id;
+
+  // Register for tab notifications.
+  registrar_.Add(this,
+                 content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+                 Source<NavigationController>(&contents()->controller()));
+
+  registrar_.Add(this,
+                 content::NOTIFICATION_TAB_CONTENTS_DESTROYED,
+                 Source<TabContents>(contents()));
+}
+
+inline TabContents* Tab::contents() {
+  return tab_->tab_contents();
+}
+
+inline TabVector* Tab::offscreen_tabs() {
+  return &offscreen_tabs_;
+}
+
+const std::string& Tab::GetExtensionId() const {
+  return extension_id_;
+}
+
+void Tab::AddOffscreenTab(OffscreenTab *tab) {
+  offscreen_tabs_.push_back(tab);
+}
+
+void Tab::RemoveOffscreenTab(OffscreenTab *tab) {
+  TabIterator it_tab = std::find(
+      offscreen_tabs_.begin(), offscreen_tabs_.end(), tab);
+  offscreen_tabs_.erase(it_tab);
+}
+
+void Tab::Observe(const int type,
+                  const NotificationSource& source,
+                  const NotificationDetails& details) {
+  DCHECK(type == content::NOTIFICATION_NAV_ENTRY_COMMITTED ||
+         type == content::NOTIFICATION_TAB_CONTENTS_DESTROYED);
+
+  delete this;
+}
+
+// Map -------------------------------------------------------------------------
+
+Map::Map() {}
+Map::~Map() {}
+
+bool Map::GetOffscreenTab(const int tab_id,
+                          ExtensionFunctionDispatcher* dispatcher,
+                          Profile* profile,
+                          OffscreenTab** offscreen_tab,
+                          std::string* error_message) {
+  // Ensure that the current tab is the parent of the offscreen tab.
+  TabContents* tab_contents = NULL;
+  if (!GetCurrentTab(dispatcher, profile, &tab_contents, error_message))
+    return false;
+
+  Tab* tab = NULL;
+  if (!GetTab(ExtensionTabUtil::GetTabId(tab_contents), &tab, error_message))
+    return false;
+  TabVector* offscreen_tabs = tab->offscreen_tabs();
+
+  for (TabIterator it = offscreen_tabs->begin();
+      it != offscreen_tabs->end(); ++it)

[sky, 2011/09/14 23:34:44]

add {} here

[alexbost, 2011/09/15 03:29:49]

Done.

+    if (ExtensionTabUtil::GetTabId((*it)->contents()) == tab_id) {
+      *offscreen_tab = *it;
+      return true;
+    }
+
+  *error_message = ExtensionErrorUtils::FormatErrorMessage(
+      keys::kOffscreenTabNotFoundError, base::IntToString(tab_id));
+  return false;
+}
+
+bool Map::GetTab(const int tab_id, Tab** tab, std::string* error_message) {
+  TabMap::iterator it = map.find(tab_id);
+
+  if (it == map.end()) {
+    *error_message = ExtensionErrorUtils::FormatErrorMessage(
+        keys::kTabNotFoundError, base::IntToString(tab_id));
+    return false;
+  }
+
+  *tab = it->second;
+
+  return true;
+}
+
+bool Map::GetTabOfOffscreenTab(TabContents* offscreen_tab_contents,
+                               Tab** tab,
+                               std::string* error_message) {
+  int offscreen_tab_id = ExtensionTabUtil::GetTabId(offscreen_tab_contents);
+
+  for (TabMap::iterator it = map.begin(); it != map.end(); ++it) {
+    TabVector* offscreen_tabs = it->second->offscreen_tabs();
+    for (TabIterator it_tab = offscreen_tabs->begin();
+         it_tab != offscreen_tabs->end(); ++it_tab) {
+      if ((*it_tab)->contents() == offscreen_tab_contents) {
+        if (!GetTab(it->first, tab, error_message))
+          return false;
+
+        return true;
+      }
+    }
+  }
+
+  *error_message = ExtensionErrorUtils::FormatErrorMessage(
+      keys::kTabOfOffscreenTabNotFoundError,
+      base::IntToString(offscreen_tab_id));
+  return false;
+}
+
+bool Map::AddOffscreenTab(OffscreenTab* offscreen_tab,
+                          ExtensionFunctionDispatcher* dispatcher,
+                          Profile* profile,
+                          const std::string& ext_id,
+                          std::string* error_message) {
+  // Get parent tab.
+  TabContents* tab_contents = NULL;
+  if (!GetCurrentTab(dispatcher, profile, &tab_contents, error_message))
+    return false;
+  int tab_id = ExtensionTabUtil::GetTabId(tab_contents);
+
+  Tab* tab = NULL;
+  if (!GetTab(tab_id, &tab, error_message)) {
+    tab = map[tab_id] = new Tab();
+    tab->Init(tab_contents, ext_id);
+  }
+
+  tab->AddOffscreenTab(offscreen_tab);
+
+  return true;
+}
+
+bool Map::RemoveOffscreenTab(const int tab_id,
+                             ExtensionFunctionDispatcher* dispatcher,
+                             Profile* profile,
+                             std::string* error_message) {
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetOffscreenTab(tab_id, dispatcher, profile,
+                       &offscreen_tab, error_message))
+    return false;
+
+  Tab* tab = NULL;
+  if (!GetTabOfOffscreenTab(offscreen_tab->contents(), &tab, error_message))
+    return false;
+
+  tab->RemoveOffscreenTab(offscreen_tab);
+
+  // If this was the last offscreen tab for the parent tab, remove the parent.
+  if (tab->offscreen_tabs()->empty())
+    map.erase(ExtensionTabUtil::GetTabId(tab->contents()));
+
+  return true;
+}
+
+bool Map::RemoveTab(const int tab_id, std::string* error_message) {
+  if (map[tab_id] == NULL) {

[sky, 2011/09/14 23:34:44]

Use find to avoid insertion.

[alexbost, 2011/09/15 03:29:49]

Done.

+    *error_message = ExtensionErrorUtils::FormatErrorMessage(
+        keys::kTabNotFoundError, base::IntToString(tab_id));
+    return false;
+  }
+
+  map.erase(tab_id);
+
+  return true;
+}
+
+}  // namespace
+
+// API functions ---------------------------------------------------------------
+
+// create ----------------------------------------------------------------------
+
+CreateOffscreenTabFunction::CreateOffscreenTabFunction() {}
+CreateOffscreenTabFunction::~CreateOffscreenTabFunction() {}
+
+bool CreateOffscreenTabFunction::RunImpl() {
+  DictionaryValue* create_props;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(0, &create_props));
+
+  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;
+  }
+
+  gfx::Rect window_bounds;
+  bool maximized;
+  if (!create_props->HasKey(keys::kWidthKey) ||
+      !create_props->HasKey(keys::kHeightKey)) {
+    Browser* browser = GetCurrentBrowser();

[sky, 2011/09/14 23:34:44]

How do you know current browser is the one you want?

[alexbost, 2011/09/15 03:29:49]

What would you use instead? Notice, we only use the browser to set default width
and height when they are not provided by the application.

[sky, 2011/09/15 20:05:57]

Maybe the size of the tab?

[alexbost, 2011/09/15 20:57:57]

Good catch.

+    if (!browser) {
+      error_ = keys::kNoCurrentWindowError;
+      return false;
+    }
+
+    WindowSizer::GetBrowserWindowBounds(std::string(), gfx::Rect(),
+                                        browser, &window_bounds,
+                                        &maximized);
+  }
+
+  int width = window_bounds.width();
+  if (create_props->HasKey(keys::kWidthKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        create_props->GetInteger(keys::kWidthKey, &width));
+
+  int height = window_bounds.height();
+  if (create_props->HasKey(keys::kHeightKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        create_props->GetInteger(keys::kHeightKey, &height));
+
+  OffscreenTab* tab = new OffscreenTab();
+  tab->Init(url, width, height, GetExtension(), profile_, dispatcher());
+
+  // Add the offscreen tab to the map so we don't lose track of it.
+  if (!GetMap()->AddOffscreenTab(tab, dispatcher(), profile_,
+                                 extension_id(), &error_)) {
+    delete tab;  // Prevent leaking of offscreen tab.
+    return false;
+  }
+
+  if (has_callback()) {
+    result_.reset(tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// get -------------------------------------------------------------------------
+
+GetOffscreenTabFunction::GetOffscreenTabFunction() {}
+GetOffscreenTabFunction::~GetOffscreenTabFunction() {}
+
+bool GetOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+
+  OffscreenTab* tab = NULL;
+  if (!GetMap()->
+      GetOffscreenTab(tab_id, dispatcher(), profile_, &tab, &error_)) {
+    error_ = ExtensionErrorUtils::FormatErrorMessage(
+      keys::kOffscreenTabNotFoundError, base::IntToString(tab_id));

[sky, 2011/09/14 23:34:44]

indent 2 more.

[alexbost, 2011/09/15 03:29:49]

Done.

+    return false;
+  }
+
+  result_.reset(tab->CreateValue());
+  SendResponse(true);
+
+  return true;
+}
+
+// getAll ----------------------------------------------------------------------
+
+GetAllOffscreenTabFunction::GetAllOffscreenTabFunction() {}
+GetAllOffscreenTabFunction::~GetAllOffscreenTabFunction() {}
+
+bool GetAllOffscreenTabFunction::RunImpl() {
+  TabContents* tab_contents = NULL;
+  if (!GetCurrentTab(dispatcher(), profile_, &tab_contents, &error_))
+    return false;
+
+  Tab* tab = NULL;
+  if (!GetMap()->
+      GetTab(ExtensionTabUtil::GetTabId(tab_contents), &tab, &error_))
+    return false;
+
+  TabVector* offscreen_tabs = tab->offscreen_tabs();
+
+  ListValue* tab_list = new ListValue();
+  for (TabIterator it_tab = offscreen_tabs->begin();
+      it_tab != offscreen_tabs->end(); ++it_tab)
+    tab_list->Append((*it_tab)->CreateValue());
+
+  result_.reset(tab_list);
+  SendResponse(true);
+
+  return true;
+}
+
+// remove ----------------------------------------------------------------------
+
+RemoveOffscreenTabFunction::RemoveOffscreenTabFunction() {}
+RemoveOffscreenTabFunction::~RemoveOffscreenTabFunction() {}
+
+bool RemoveOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+
+  OffscreenTab* tab = NULL;
+  if (!GetMap()->GetOffscreenTab(tab_id, dispatcher(), profile_, &tab, &error_))
+    return false;
+
+  if (!GetMap()->RemoveOffscreenTab(tab_id, dispatcher(), profile_, &error_))
+    return false;
+
+  delete tab;
+
+  return true;
+}
+
+// sendKeyboardEvent -----------------------------------------------------------
+
+SendKeyboardEventOffscreenTabFunction::
+    SendKeyboardEventOffscreenTabFunction() {}
+SendKeyboardEventOffscreenTabFunction::
+    ~SendKeyboardEventOffscreenTabFunction() {}
+
+bool SendKeyboardEventOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+
+  OffscreenTab* tab = NULL;
+  if (!GetMap()->GetOffscreenTab(tab_id, dispatcher(), profile_, &tab, &error_))
+    return false;
+
+  // JavaScript KeyboardEvent.
+  DictionaryValue* dict = NULL;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &dict));
+
+  NativeWebKeyboardEvent keyboard_event;
+
+  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;
+  }
+
+  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;
+  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;
+    }
+  }
+
+  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 the event.
+  tab->contents()->render_view_host()->
+      ForwardKeyboardEvent(keyboard_event);
+
+  if (has_callback()) {
+    result_.reset(tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// sendMouseEvent --------------------------------------------------------------
+
+SendMouseEventOffscreenTabFunction::SendMouseEventOffscreenTabFunction() {}
+SendMouseEventOffscreenTabFunction::~SendMouseEventOffscreenTabFunction() {}
+
+bool SendMouseEventOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+
+  OffscreenTab* tab = NULL;
+  if (!GetMap()->GetOffscreenTab(tab_id, dispatcher(), profile_, &tab, &error_))
+    return false;
+
+  // JavaScript MouseEvent.
+  DictionaryValue* dict = NULL;
+  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;
+
+    wheel_event.type = WebInputEvent::MouseWheel;
+
+    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->contents()->render_view_host()->ForwardWheelEvent(wheel_event);
+  } else {
+    WebKit::WebMouseEvent mouse_event;
+
+    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;
+    }
+
+    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;
+    }
+
+    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;
+    }
+
+    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;
+
+    mouse_event.clickCount = 1;
+
+    // Forward the event.
+    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->contents()->render_view_host()->ForwardMouseEvent(mouse_event);
+    }
+  }
+
+  if (has_callback()) {
+    result_.reset(tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// toDataUrl -------------------------------------------------------------------
+
+ToDataUrlOffscreenTabFunction::ToDataUrlOffscreenTabFunction() {}
+ToDataUrlOffscreenTabFunction::~ToDataUrlOffscreenTabFunction() {}
+
+// 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 in order to get offscreen tabs in O(1).
+bool ToDataUrlOffscreenTabFunction::RunImpl() {
+  int tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &tab_id));
+
+
+  OffscreenTab* tab = NULL;
+  if (!GetMap()->GetOffscreenTab(tab_id, dispatcher(), profile_, &tab, &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->contents()->GetURL(), &error_))
+    return false;
+
+// The backing store approach works on Linux but not on Mac.
+// TODO(alexbost): Test on Windows
+#if !defined(OS_MACOSX)
+  RenderViewHost* render_view_host = 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.
+  TabContentsWrapper* tab_wrapper =
+      TabContentsWrapper::GetCurrentWrapperForContents(tab->contents());
+  tab_wrapper->CaptureSnapshot();
+  registrar_.Add(this,
+               chrome::NOTIFICATION_TAB_SNAPSHOT_TAKEN,
+               Source<TabContentsWrapper>(tab_wrapper));
+
+  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() {}
+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));
+
+  OffscreenTab* tab = NULL;
+  if (!GetMap()->GetOffscreenTab(tab_id, dispatcher(), profile_, &tab, &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->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->contents()->render_view_host();
+      render_view_host->Send(
+          new ExtensionMsg_ExecuteCode(render_view_host->routing_id(),
+                                       params));
+
+      Observe(tab->contents());
+      AddRef();  // balanced in Observe()
+
+      return true;
+    }
+
+    tab->SetUrl(url);
+
+    // 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->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
+      GetTabSize(TabContentsWrapper::GetCurrentWrapperForContents(
+          tab->contents())).width();
+
+    int height;
+    if (update_props->HasKey(keys::kHeightKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          update_props->GetInteger(keys::kHeightKey, &height));
+    else
+      GetTabSize(TabContentsWrapper::GetCurrentWrapperForContents(
+          tab->contents())).height();
+
+    tab->SetSize(width, height);
+  }
+
+  // Callback
+  if (has_callback()) {
+    result_.reset(tab->CreateValue());
+    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()
+}
+