Revert 131452 - Add GLHelper::AsyncCopyTextureTo and make thumbnail generation asynchronous.

BUG=118547
TEST=Manually checked that UI thread is not blocked by the thumbnailer


Review URL: http://codereview.chromium.org/9791031

TBR=mazda@chromium.org
Review URL: https://chromiumcodereview.appspot.com/10024036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@131456 0039d316-1c4b-4281-b951-d872f2087c98

21 files changed, 157 insertions, 624 deletions

diff --git a/chrome/browser/tab_contents/thumbnail_generator.cc b/chrome/browser/tab_contents/thumbnail_generator.cc
index ba85037..eeb2bfb 100644
--- a/chrome/browser/tab_contents/thumbnail_generator.cc
+++ b/chrome/browser/tab_contents/thumbnail_generator.cc
@@ -16,7 +16,6 @@
 #include "chrome/browser/history/top_sites.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/thumbnail_score.h"
-#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
@@ -87,16 +86,33 @@ gfx::Size GetCopySizeForThumbnail(const gfx::Size& view_size,
                    static_cast<int>(scale * view_size.height()));
 }
 
-// Creates a downsampled thumbnail from the given bitmap.
+// Creates a downsampled thumbnail for the given RenderWidgetHost's backing
 // store. The returned bitmap will be isNull if there was an error creating it.
-SkBitmap CreateThumbnail(
-    const SkBitmap& bmp_with_scrollbars,
+SkBitmap GetBitmapForRenderWidgetHost(
+    RenderWidgetHost* render_widget_host,
     int desired_width,
     int desired_height,
     int options,
     ThumbnailGenerator::ClipResult* clip_result) {
   base::TimeTicks begin_compute_thumbnail = base::TimeTicks::Now();
 
+  SkBitmap result;
+
+  // Get the bitmap as a Skia object so we can resample it. This is a large
+  // allocation and we can tolerate failure here, so give up if the allocation
+  // fails.
+  skia::PlatformCanvas temp_canvas;
+  content::RenderWidgetHostView* view = render_widget_host->GetView();
+  if (!view)
+    return result;
+  const gfx::Size copy_size =
+      GetCopySizeForThumbnail(view->GetViewBounds().size(),
+                              gfx::Size(desired_width, desired_height));
+  if (!render_widget_host->CopyFromBackingStore(
+          gfx::Rect(), copy_size, &temp_canvas))
+    return result;
+  const SkBitmap& bmp_with_scrollbars =
+      skia::GetTopDevice(temp_canvas)->accessBitmap(false);
   // Clip the edgemost 15 pixels as that will commonly hold a scrollbar, which
   // looks bad in thumbnails.
   SkIRect scrollbarless_rect =
@@ -105,7 +121,7 @@ SkBitmap CreateThumbnail(
         std::max(1, bmp_with_scrollbars.height() - 15) };
   SkBitmap bmp;
   bmp_with_scrollbars.extractSubset(&bmp, scrollbarless_rect);
-  SkBitmap result;
+
   // Check if a clipped thumbnail is requested.
   if (options & ThumbnailGenerator::kClippedThumbnail) {
     SkBitmap clipped_bitmap = ThumbnailGenerator::GetClippedBitmap(
@@ -151,37 +167,6 @@ SkBitmap CreateThumbnail(
   return result;
 }
 
-// Creates a downsampled thumbnail for the given RenderWidgetHost's backing
-// store. The returned bitmap will be isNull if there was an error creating it.
-SkBitmap GetBitmapForRenderWidgetHost(
-    RenderWidgetHost* render_widget_host,
-    int desired_width,
-    int desired_height,
-    int options,
-    ThumbnailGenerator::ClipResult* clip_result) {
-  // base::TimeTicks begin_compute_thumbnail = base::TimeTicks::Now();
-
-  // Get the bitmap as a Skia object so we can resample it. This is a large
-  // allocation and we can tolerate failure here, so give up if the allocation
-  // fails.
-  skia::PlatformCanvas temp_canvas;
-  content::RenderWidgetHostView* view = render_widget_host->GetView();
-  if (!view)
-    return SkBitmap();
-  const gfx::Size copy_size =
-      GetCopySizeForThumbnail(view->GetViewBounds().size(),
-                              gfx::Size(desired_width, desired_height));
-  if (!render_widget_host->CopyFromBackingStore(
-          gfx::Rect(), copy_size, &temp_canvas))
-    return SkBitmap();
-
-  return CreateThumbnail(skia::GetTopDevice(temp_canvas)->accessBitmap(false),
-                         desired_width,
-                         desired_height,
-                         options,
-                         clip_result);
-}
-
 }  // namespace
 
 struct ThumbnailGenerator::AsyncRequestInfo {
@@ -191,8 +176,7 @@ struct ThumbnailGenerator::AsyncRequestInfo {
 };
 
 ThumbnailGenerator::ThumbnailGenerator()
-    : load_interrupted_(false),
-      weak_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+    : load_interrupted_(false) {
   // The BrowserProcessImpl creates this non-lazily. If you add nontrivial
   // stuff here, be sure to convert it to being lazily created.
   //
@@ -427,9 +411,6 @@ void ThumbnailGenerator::WebContentsDisconnected(WebContents* contents) {
     }
     ++iterator;
   }
-
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
-  web_contents_weak_factory_.reset(NULL);
 }
 
 double ThumbnailGenerator::CalculateBoringScore(const SkBitmap& bitmap) {
@@ -505,7 +486,15 @@ void ThumbnailGenerator::UpdateThumbnailIfNecessary(
   if (!ShouldUpdateThumbnail(profile, top_sites, url))
     return;
 
-  AsyncUpdateThumbnail(web_contents);
+  const int options = ThumbnailGenerator::kClippedThumbnail;
+  ThumbnailGenerator::ClipResult clip_result = ThumbnailGenerator::kNotClipped;
+  SkBitmap thumbnail = GetThumbnailForRendererWithOptions(
+      web_contents->GetRenderViewHost(), options, &clip_result);
+  // Failed to generate a thumbnail. Maybe the tab is in the background?
+  if (thumbnail.isNull())
+    return;
+
+  UpdateThumbnail(web_contents, thumbnail, clip_result);
 }
 
 void ThumbnailGenerator::UpdateThumbnail(
@@ -535,47 +524,6 @@ void ThumbnailGenerator::UpdateThumbnail(
   VLOG(1) << "Thumbnail taken for " << url << ": " << score.ToString();
 }
 
-void ThumbnailGenerator::AsyncUpdateThumbnail(
-    WebContents* web_contents) {
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
-  RenderWidgetHost* render_widget_host = web_contents->GetRenderViewHost();
-  content::RenderWidgetHostView* view = render_widget_host->GetView();
-  if (!view)
-    return;
-
-  const gfx::Size copy_size =
-      GetCopySizeForThumbnail(view->GetViewBounds().size(),
-                              gfx::Size(kThumbnailWidth, kThumbnailHeight));
-  skia::PlatformCanvas* temp_canvas = new skia::PlatformCanvas;
-  web_contents_weak_factory_.reset(
-      new base::WeakPtrFactory<WebContents>(web_contents));
-  render_widget_host->AsyncCopyFromBackingStore(
-      gfx::Rect(), copy_size, temp_canvas,
-      base::Bind(&ThumbnailGenerator::AsyncUpdateThumbnailFinish,
-                 weak_factory_.GetWeakPtr(),
-                 web_contents_weak_factory_->GetWeakPtr(),
-                 base::Owned(temp_canvas)));
-}
-
-void ThumbnailGenerator::AsyncUpdateThumbnailFinish(
-    base::WeakPtr<WebContents> web_contents,
-    skia::PlatformCanvas* temp_canvas,
-    bool succeeded) {
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
-  if (!succeeded)
-    return;
-
-  SkBitmap bmp_with_scrollbars =
-      skia::GetTopDevice(*temp_canvas)->accessBitmap(false);
-  ClipResult clip_result;
-  SkBitmap thumbnail = CreateThumbnail(bmp_with_scrollbars,
-                                       kThumbnailWidth,
-                                       kThumbnailHeight,
-                                       ThumbnailGenerator::kClippedThumbnail,
-                                       &clip_result);
-  UpdateThumbnail(web_contents.get(), thumbnail, clip_result);
-}
-
 bool ThumbnailGenerator::ShouldUpdateThumbnail(Profile* profile,
                                                history::TopSites* top_sites,
                                                const GURL& url) {
diff --git a/chrome/browser/tab_contents/thumbnail_generator.h b/chrome/browser/tab_contents/thumbnail_generator.h
index 0ea0be4..481e5da 100644
--- a/chrome/browser/tab_contents/thumbnail_generator.h
+++ b/chrome/browser/tab_contents/thumbnail_generator.h
@@ -13,7 +13,6 @@
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/memory/linked_ptr.h"
-#include "base/memory/weak_ptr.h"
 #include "base/timer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -35,10 +34,6 @@ namespace history {
 class TopSites;
 }
 
-namespace skia {
-class PlatformCanvas;
-}
-
 class ThumbnailGenerator : public content::NotificationObserver,
                            public content::WebContentsObserver {
  public:
@@ -151,17 +146,6 @@ class ThumbnailGenerator : public content::NotificationObserver,
       int tag,
       const gfx::Size& size);
 
-  // Asynchronously updates the thumbnail of the given tab. This must be called
-  // on the UI thread.
-  void AsyncUpdateThumbnail(content::WebContents* web_contents);
-
-  // Called when the bitmap for generating a thumbnail is ready after the
-  // AsyncUpdateThumbnail invocation. This runs on the UI thread.
-  void AsyncUpdateThumbnailFinish(
-      base::WeakPtr<content::WebContents> web_contents,
-      skia::PlatformCanvas* temp_canvas,
-      bool result);
-
   // content::NotificationObserver interface.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
@@ -184,10 +168,6 @@ class ThumbnailGenerator : public content::NotificationObserver,
 
   bool load_interrupted_;
 
-  base::WeakPtrFactory<ThumbnailGenerator> weak_factory_;
-  scoped_ptr<base::WeakPtrFactory<content::WebContents> >
-      web_contents_weak_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(ThumbnailGenerator);
 };
 
diff --git a/content/browser/renderer_host/image_transport_factory.cc b/content/browser/renderer_host/image_transport_factory.cc
index a25ca60..d000c7d 100644
--- a/content/browser/renderer_host/image_transport_factory.cc
+++ b/content/browser/renderer_host/image_transport_factory.cc
@@ -243,12 +243,25 @@ class GpuProcessTransportFactory : public ui::ContextFactory,
 
   virtual WebKit::WebGraphicsContext3D* CreateContext(
       ui::Compositor* compositor) OVERRIDE {
-    return CreateContextCommon(compositor, false);
-  }
+    PerCompositorData* data = per_compositor_data_[compositor];
+    if (!data)
+      data = CreatePerCompositorData(compositor);
 
-  virtual WebKit::WebGraphicsContext3D* CreateOffscreenContext(
-      ui::Compositor* compositor) OVERRIDE {
-    return CreateContextCommon(compositor, true);
+    WebKit::WebGraphicsContext3D::Attributes attrs;
+    attrs.shareResources = true;
+    GpuChannelHostFactory* factory = BrowserGpuChannelHostFactory::instance();
+    scoped_ptr<WebGraphicsContext3DCommandBufferImpl> context(
+        new WebGraphicsContext3DCommandBufferImpl(
+            data->surface_id,
+            GURL(),
+            factory,
+            data->swap_client->AsWeakPtr()));
+    if (!context->Initialize(
+        attrs,
+        false,
+        content::CAUSE_FOR_GPU_LAUNCH_WEBGRAPHICSCONTEXT3DCOMMANDBUFFERIMPL_INITIALIZE))
+      return NULL;
+    return context.release();
   }
 
   virtual void RemoveCompositor(ui::Compositor* compositor) OVERRIDE {
@@ -373,30 +386,6 @@ class GpuProcessTransportFactory : public ui::ContextFactory,
     return data;
   }
 
-  WebKit::WebGraphicsContext3D* CreateContextCommon(
-      ui::Compositor* compositor,
-      bool offscreen) OVERRIDE {
-    PerCompositorData* data = per_compositor_data_[compositor];
-    if (!data)
-      data = CreatePerCompositorData(compositor);
-
-    WebKit::WebGraphicsContext3D::Attributes attrs;
-    attrs.shareResources = true;
-    GpuChannelHostFactory* factory = BrowserGpuChannelHostFactory::instance();
-    scoped_ptr<WebGraphicsContext3DCommandBufferImpl> context(
-        new WebGraphicsContext3DCommandBufferImpl(
-            offscreen ? 0 : data->surface_id,
-            GURL(),
-            factory,
-            data->swap_client->AsWeakPtr()));
-    if (!context->Initialize(
-        attrs,
-        false,
-        content::CAUSE_FOR_GPU_LAUNCH_WEBGRAPHICSCONTEXT3DCOMMANDBUFFERIMPL_INITIALIZE))
-      return NULL;
-    return context.release();
-  }
-
   void CreateSharedContext(ui::Compositor* compositor) {
     PerCompositorData* data = per_compositor_data_[compositor];
     DCHECK(data);
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index fd5e142..7476989 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -514,40 +514,6 @@ bool RenderWidgetHostImpl::CopyFromBackingStore(
   return backing_store->CopyFromBackingStore(copy_rect, output);
 }
 
-void RenderWidgetHostImpl::AsyncCopyFromBackingStore(
-    const gfx::Rect& src_rect,
-    const gfx::Size& accelerated_dest_size,
-    skia::PlatformCanvas* output,
-    base::Callback<void(bool)> callback) {
-  if (view_ && is_accelerated_compositing_active_) {
-    TRACE_EVENT0("browser",
-        "RenderWidgetHostImpl::CopyFromBackingStore::FromCompositingSurface");
-    // TODO(mazda): Support partial copy with |src_rect|
-    // (http://crbug.com/118571).
-    view_->AsyncCopyFromCompositingSurface(accelerated_dest_size,
-                                           output,
-                                           callback);
-    return;
-  }
-
-  BackingStore* backing_store = GetBackingStore(false);
-  if (!backing_store) {
-    callback.Run(false);
-    return;
-  }
-
-  TRACE_EVENT0("browser",
-      "RenderWidgetHostImpl::CopyFromBackingStore::FromBackingStore");
-  const gfx::Size backing_store_size = backing_store->size();
-  gfx::Rect copy_rect = src_rect.IsEmpty() ?
-      gfx::Rect(0, 0, backing_store_size.width(), backing_store_size.height()) :
-      src_rect;
-  // When the result size is equal to the backing store size, copy from the
-  // backing store directly to the output canvas.
-  bool result = backing_store->CopyFromBackingStore(copy_rect, output);
-  callback.Run(result);
-}
-
 #if defined(TOOLKIT_GTK)
 bool RenderWidgetHostImpl::CopyFromBackingStoreToGtkWindow(
     const gfx::Rect& dest_rect, GdkWindow* target) {
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index b66a6cd..ca16dbc5 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -81,11 +81,6 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   virtual bool CopyFromBackingStore(const gfx::Rect& src_rect,
                                     const gfx::Size& accelerated_dest_size,
                                     skia::PlatformCanvas* output) OVERRIDE;
-  virtual void AsyncCopyFromBackingStore(
-      const gfx::Rect& src_rect,
-      const gfx::Size& accelerated_dest_size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) OVERRIDE;
 #if defined(TOOLKIT_GTK)
   virtual bool CopyFromBackingStoreToGtkWindow(const gfx::Rect& dest_rect,
                                                GdkWindow* target) OVERRIDE;
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 89c1d03..0b7665a 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -5,7 +5,6 @@
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include "base/bind.h"
-#include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "content/browser/renderer_host/backing_store_skia.h"
@@ -101,18 +100,6 @@ bool CanRendererHandleEvent(const aura::MouseEvent* event) {
   return true;
 }
 
-// Creates a content::GLHelper for the given compositor.
-content::GLHelper* CreateGLHelper(ui::Compositor* compositor) {
-  ImageTransportFactory* factory = ImageTransportFactory::GetInstance();
-  WebKit::WebGraphicsContext3D* context =
-      factory->GetSharedContext(compositor);
-  DCHECK(context);
-  WebKit::WebGraphicsContext3D* context_for_thread =
-      factory->AsContextFactory()->CreateOffscreenContext(compositor);
-  DCHECK(context_for_thread);
-  return new content::GLHelper(context, context_for_thread);
-}
-
 }  // namespace
 
 // We have to implement the WindowObserver interface on a separate object
@@ -416,60 +403,6 @@ BackingStore* RenderWidgetHostViewAura::AllocBackingStore(
   return new BackingStoreSkia(host_, size);
 }
 
-bool RenderWidgetHostViewAura::CopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output) {
-  ui::Compositor* compositor = GetCompositor();
-  if (!compositor)
-    return false;
-
-  ImageTransportClient* container = image_transport_clients_[current_surface_];
-  if (!container)
-    return false;
-
-  if (!output->initialize(size.width(), size.height(), true))
-    return false;
-
-  if (!gl_helper_.get())
-    gl_helper_.reset(CreateGLHelper(compositor));
-
-  unsigned char* addr = static_cast<unsigned char*>(
-      output->getTopDevice()->accessBitmap(true).getPixels());
-  return gl_helper_->CopyTextureTo(container->texture_id(),
-                                   container->size(),
-                                   size,
-                                   addr);
-}
-
-void RenderWidgetHostViewAura::AsyncCopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output,
-    base::Callback<void(bool)> callback) {
-  base::ScopedClosureRunner scoped_callback_runner(base::Bind(callback, false));
-  ui::Compositor* compositor = GetCompositor();
-  if (!compositor)
-    return;
-
-  ImageTransportClient* container = image_transport_clients_[current_surface_];
-  if (!container)
-    return;
-
-  if (!output->initialize(size.width(), size.height(), true))
-    return;
-
-  if (!gl_helper_.get())
-    gl_helper_.reset(CreateGLHelper(compositor));
-
-  scoped_callback_runner.Release();
-  unsigned char* addr = static_cast<unsigned char*>(
-      output->getTopDevice()->accessBitmap(true).getPixels());
-  gl_helper_->AsyncCopyTextureTo(container->texture_id(),
-                                 container->size(),
-                                 size,
-                                 addr,
-                                 callback);
-}
-
 void RenderWidgetHostViewAura::OnAcceleratedCompositingStateChange() {
   // Delay UpdateExternalTexture until we actually got a software frame.
   // Sometimes (e.g. on a page load) the renderer will spuriously disable then
@@ -639,6 +572,36 @@ void RenderWidgetHostViewAura::SetBackground(const SkBitmap& background) {
   window_->layer()->SetFillsBoundsOpaquely(background.isOpaque());
 }
 
+bool RenderWidgetHostViewAura::CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) {
+  ui::Compositor* compositor = GetCompositor();
+  if (!compositor)
+    return false;
+
+  ImageTransportFactory* factory = ImageTransportFactory::GetInstance();
+  WebKit::WebGraphicsContext3D* context = factory->GetSharedContext(compositor);
+  if (!context)
+    return false;
+
+  ImageTransportClient* container = image_transport_clients_[current_surface_];
+  if (!container)
+    return false;
+
+  if (!output->initialize(size.width(), size.height(), true))
+    return false;
+
+  if (!gl_helper_.get())
+    gl_helper_.reset(new content::GLHelper(context));
+
+  unsigned char* addr = static_cast<unsigned char*>(
+      output->getTopDevice()->accessBitmap(true).getPixels());
+  return gl_helper_->CopyTextureTo(container->texture_id(),
+                                   container->size(),
+                                   size,
+                                   addr);
+}
+
 void RenderWidgetHostViewAura::GetScreenInfo(WebKit::WebScreenInfo* results) {
   GetDefaultScreenInfo(results);
 }
@@ -1149,7 +1112,8 @@ void RenderWidgetHostViewAura::OnLostResources(ui::Compositor* compositor) {
     // Detach the resources to avoid deleting them using the invalid context.
     // They've been released anyway when the GPU process died.
     gl_helper_->Detach();
-    gl_helper_.reset(CreateGLHelper(compositor));
+    gl_helper_.reset(
+        new content::GLHelper(factory->GetSharedContext(compositor)));
   }
 }
 
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 0127f1e..49479b0 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -66,6 +66,9 @@ class RenderWidgetHostViewAura
   virtual bool IsShowing() OVERRIDE;
   virtual gfx::Rect GetViewBounds() const OVERRIDE;
   virtual void SetBackground(const SkBitmap& background) OVERRIDE;
+  virtual bool CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) OVERRIDE;
 
   // Overridden from RenderWidgetHostViewPort:
   virtual void InitAsPopup(content::RenderWidgetHostView* parent_host_view,
@@ -93,13 +96,6 @@ class RenderWidgetHostViewAura
   virtual void SelectionBoundsChanged(const gfx::Rect& start_rect,
                                       const gfx::Rect& end_rect) OVERRIDE;
   virtual BackingStore* AllocBackingStore(const gfx::Size& size) OVERRIDE;
-  virtual bool CopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output) OVERRIDE;
-  virtual void AsyncCopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) OVERRIDE;
   virtual void OnAcceleratedCompositingStateChange() OVERRIDE;
   virtual void AcceleratedSurfaceBuffersSwapped(
       const GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params& params,
diff --git a/content/browser/renderer_host/render_widget_host_view_gtk.cc b/content/browser/renderer_host/render_widget_host_view_gtk.cc
index 7c5fcdf..b49e8d6 100644
--- a/content/browser/renderer_host/render_widget_host_view_gtk.cc
+++ b/content/browser/renderer_host/render_widget_host_view_gtk.cc
@@ -969,23 +969,6 @@ BackingStore* RenderWidgetHostViewGtk::AllocBackingStore(
                              depth);
 }
 
-bool RenderWidgetHostViewGtk::CopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output) {
-  // TODO(mazda): Implement this.
-  NOTIMPLEMENTED();
-  return false;
-}
-
-void RenderWidgetHostViewGtk::AsyncCopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output,
-    base::Callback<void(bool)> callback) {
-  // TODO(mazda): Implement this.
-  NOTIMPLEMENTED();
-  callback.Run(false);
-}
-
 void RenderWidgetHostViewGtk::AcceleratedSurfaceBuffersSwapped(
     const GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params& params,
     int gpu_host_id) {
@@ -1007,6 +990,14 @@ void RenderWidgetHostViewGtk::SetBackground(const SkBitmap& background) {
   host_->Send(new ViewMsg_SetBackground(host_->GetRoutingID(), background));
 }
 
+bool RenderWidgetHostViewGtk::CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) {
+  // TODO(mazda): Implement this.
+  NOTIMPLEMENTED();
+  return false;
+}
+
 void RenderWidgetHostViewGtk::ModifyEventForEdgeDragging(
     GtkWidget* widget, GdkEventMotion* event) {
   // If the widget is aligned with an edge of the monitor its on and the user
diff --git a/content/browser/renderer_host/render_widget_host_view_gtk.h b/content/browser/renderer_host/render_widget_host_view_gtk.h
index 71c080d..b943a8d 100644
--- a/content/browser/renderer_host/render_widget_host_view_gtk.h
+++ b/content/browser/renderer_host/render_widget_host_view_gtk.h
@@ -62,6 +62,9 @@ class RenderWidgetHostViewGtk : public content::RenderWidgetHostViewBase {
   virtual GdkEventButton* GetLastMouseDown() OVERRIDE;
   virtual gfx::NativeView BuildInputMethodsGtkMenu() OVERRIDE;
   virtual void SetBackground(const SkBitmap& background) OVERRIDE;
+  virtual bool CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) OVERRIDE;
 
   // RenderWidgetHostViewPort implementation.
   virtual void InitAsPopup(content::RenderWidgetHostView* parent_host_view,
@@ -93,13 +96,6 @@ class RenderWidgetHostViewGtk : public content::RenderWidgetHostViewBase {
   virtual void SelectionBoundsChanged(const gfx::Rect& start_rect,
                                       const gfx::Rect& end_rect) OVERRIDE;
   virtual BackingStore* AllocBackingStore(const gfx::Size& size) OVERRIDE;
-  virtual bool CopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output) OVERRIDE;
-  virtual void AsyncCopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) OVERRIDE;
   virtual void OnAcceleratedCompositingStateChange() OVERRIDE;
   virtual void AcceleratedSurfaceBuffersSwapped(
       const GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params& params,
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.h b/content/browser/renderer_host/render_widget_host_view_mac.h
index 4df271b..2cb053e 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.h
+++ b/content/browser/renderer_host/render_widget_host_view_mac.h
@@ -206,6 +206,9 @@ class RenderWidgetHostViewMac : public content::RenderWidgetHostViewBase {
   virtual void SetWindowVisibility(bool visible) OVERRIDE;
   virtual void WindowFrameChanged() OVERRIDE;
   virtual void SetBackground(const SkBitmap& background) OVERRIDE;
+  virtual bool CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) OVERRIDE;
 
   // Implementation of RenderWidgetHostViewPort.
   virtual void InitAsPopup(content::RenderWidgetHostView* parent_host_view,
@@ -237,13 +240,6 @@ class RenderWidgetHostViewMac : public content::RenderWidgetHostViewBase {
                                 size_t offset,
                                 const ui::Range& range) OVERRIDE;
   virtual BackingStore* AllocBackingStore(const gfx::Size& size) OVERRIDE;
-  virtual bool CopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output) OVERRIDE;
-  virtual void AsyncCopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) OVERRIDE;
   virtual void OnAcceleratedCompositingStateChange() OVERRIDE;
   // See comment in RenderWidgetHostView!
   virtual gfx::Rect GetViewCocoaBounds() const OVERRIDE;
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 6ba515f..2138fa7 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -793,23 +793,6 @@ BackingStore* RenderWidgetHostViewMac::AllocBackingStore(
   return new BackingStoreMac(render_widget_host_, size);
 }
 
-bool RenderWidgetHostViewMac::CopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output) {
-  // TODO(mazda): Implement this.
-  NOTIMPLEMENTED();
-  return false;
-}
-
-void RenderWidgetHostViewMac::AsyncCopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output,
-    base::Callback<void(bool)> callback) {
-  // TODO(mazda): Implement this.
-  NOTIMPLEMENTED();
-  callback.Run(false);
-}
-
 // Sets whether or not to accept first responder status.
 void RenderWidgetHostViewMac::SetTakesFocusOnlyOnMouseDown(bool flag) {
   [cocoa_view_ setTakesFocusOnlyOnMouseDown:flag];
@@ -1180,6 +1163,14 @@ void RenderWidgetHostViewMac::SetBackground(const SkBitmap& background) {
         render_widget_host_->GetRoutingID(), background));
 }
 
+bool RenderWidgetHostViewMac::CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) {
+  // TODO(mazda): Implement this.
+  NOTIMPLEMENTED();
+  return false;
+}
+
 void RenderWidgetHostViewMac::OnAccessibilityNotifications(
     const std::vector<AccessibilityHostMsg_NotificationParams>& params) {
   if (!GetBrowserAccessibilityManager()) {
diff --git a/content/browser/renderer_host/render_widget_host_view_win.cc b/content/browser/renderer_host/render_widget_host_view_win.cc
index 8ee1da2..530e5c3 100644
--- a/content/browser/renderer_host/render_widget_host_view_win.cc
+++ b/content/browser/renderer_host/render_widget_host_view_win.cc
@@ -903,6 +903,11 @@ BackingStore* RenderWidgetHostViewWin::AllocBackingStore(
   return new BackingStoreWin(render_widget_host_, size);
 }
 
+void RenderWidgetHostViewWin::SetBackground(const SkBitmap& background) {
+  content::RenderWidgetHostViewBase::SetBackground(background);
+  render_widget_host_->SetBackground(background);
+}
+
 bool RenderWidgetHostViewWin::CopyFromCompositingSurface(
       const gfx::Size& size,
       skia::PlatformCanvas* output) {
@@ -919,20 +924,6 @@ bool RenderWidgetHostViewWin::CopyFromCompositingSurface(
       size, output->getTopDevice()->accessBitmap(true).getPixels());
 }
 
-void RenderWidgetHostViewWin::AsyncCopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output,
-    base::Callback<void(bool)> callback) {
-  // TODO(mazda): Implement this.
-  NOTIMPLEMENTED();
-  callback.Run(false);
-}
-
-void RenderWidgetHostViewWin::SetBackground(const SkBitmap& background) {
-  content::RenderWidgetHostViewBase::SetBackground(background);
-  render_widget_host_->SetBackground(background);
-}
-
 void RenderWidgetHostViewWin::ProcessTouchAck(
     WebKit::WebInputEvent::Type type, bool processed) {
   if (type == WebKit::WebInputEvent::TouchStart)
diff --git a/content/browser/renderer_host/render_widget_host_view_win.h b/content/browser/renderer_host/render_widget_host_view_win.h
index 44dbfcb..08829ad 100644
--- a/content/browser/renderer_host/render_widget_host_view_win.h
+++ b/content/browser/renderer_host/render_widget_host_view_win.h
@@ -169,6 +169,9 @@ class RenderWidgetHostViewWin
   virtual bool IsShowing() OVERRIDE;
   virtual gfx::Rect GetViewBounds() const OVERRIDE;
   virtual void SetBackground(const SkBitmap& background) OVERRIDE;
+  virtual bool CopyFromCompositingSurface(
+      const gfx::Size& size,
+      skia::PlatformCanvas* output) OVERRIDE;
 
   // Implementation of RenderWidgetHostViewPort.
   virtual void InitAsPopup(content::RenderWidgetHostView* parent_host_view,
@@ -199,13 +202,6 @@ class RenderWidgetHostViewWin
   virtual void Destroy() OVERRIDE;
   virtual void SetTooltipText(const string16& tooltip_text) OVERRIDE;
   virtual BackingStore* AllocBackingStore(const gfx::Size& size) OVERRIDE;
-  virtual bool CopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output) OVERRIDE;
-  virtual void AsyncCopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) OVERRIDE;
   virtual void OnAcceleratedCompositingStateChange() OVERRIDE;
   virtual void ProcessTouchAck(WebKit::WebInputEvent::Type type,
                                bool processed) OVERRIDE;
diff --git a/content/browser/renderer_host/test_render_view_host.cc b/content/browser/renderer_host/test_render_view_host.cc
index 03d9656..791fa17 100644
--- a/content/browser/renderer_host/test_render_view_host.cc
+++ b/content/browser/renderer_host/test_render_view_host.cc
@@ -94,19 +94,6 @@ BackingStore* TestRenderWidgetHostView::AllocBackingStore(
   return new TestBackingStore(rwh_, size);
 }
 
-bool TestRenderWidgetHostView::CopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output) {
-  return false;
-}
-
-void TestRenderWidgetHostView::AsyncCopyFromCompositingSurface(
-    const gfx::Size& size,
-    skia::PlatformCanvas* output,
-    base::Callback<void(bool)> callback) {
-  callback.Run(false);
-}
-
 void TestRenderWidgetHostView::OnAcceleratedCompositingStateChange() {
 }
 
@@ -192,6 +179,12 @@ gfx::NativeView TestRenderWidgetHostView::BuildInputMethodsGtkMenu() {
 }
 #endif  // defined(TOOLKIT_GTK)
 
+bool TestRenderWidgetHostView::CopyFromCompositingSurface(
+    const gfx::Size& size,
+    skia::PlatformCanvas* output) {
+  return false;
+}
+
 gfx::GLSurfaceHandle TestRenderWidgetHostView::GetCompositingSurface() {
   return gfx::GLSurfaceHandle();
 }
diff --git a/content/browser/renderer_host/test_render_view_host.h b/content/browser/renderer_host/test_render_view_host.h
index b3837e5..365a05b 100644
--- a/content/browser/renderer_host/test_render_view_host.h
+++ b/content/browser/renderer_host/test_render_view_host.h
@@ -71,6 +71,9 @@ class TestRenderWidgetHostView : public RenderWidgetHostViewBase {
   virtual GdkEventButton* GetLastMouseDown() OVERRIDE;
   virtual gfx::NativeView BuildInputMethodsGtkMenu() OVERRIDE;
 #endif  // defined(TOOLKIT_GTK)
+  virtual bool CopyFromCompositingSurface(
+      const gfx::Size& size,
+             skia::PlatformCanvas* output) OVERRIDE;
 
   // RenderWidgetHostViewPort implementation.
   virtual void InitAsPopup(RenderWidgetHostView* parent_host_view,
@@ -97,13 +100,6 @@ class TestRenderWidgetHostView : public RenderWidgetHostViewBase {
   virtual void Destroy() OVERRIDE {}
   virtual void SetTooltipText(const string16& tooltip_text) OVERRIDE {}
   virtual BackingStore* AllocBackingStore(const gfx::Size& size) OVERRIDE;
-  virtual bool CopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output) OVERRIDE;
-  virtual void AsyncCopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) OVERRIDE;
   virtual void OnAcceleratedCompositingStateChange() OVERRIDE;
   virtual void AcceleratedSurfaceBuffersSwapped(
       const GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params& params,
diff --git a/content/common/gpu/client/gl_helper.cc b/content/common/gpu/client/gl_helper.cc
index ca91b84..5b88e4f 100644
--- a/content/common/gpu/client/gl_helper.cc
+++ b/content/common/gpu/client/gl_helper.cc
@@ -4,12 +4,7 @@
 
 #include "content/common/gpu/client/gl_helper.h"
 
-#include "base/bind.h"
-#include "base/lazy_instance.h"
 #include "base/logging.h"
-#include "base/message_loop.h"
-#include "base/synchronization/waitable_event.h"
-#include "base/threading/thread.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebCString.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebString.h"
 #include "ui/gfx/gl/gl_bindings.h"
@@ -17,21 +12,6 @@
 
 namespace {
 
-const char kGLHelperThreadName[] = "GLHelperThread";
-
-class GLHelperThread : public base::Thread {
- public:
-  GLHelperThread() : base::Thread(kGLHelperThreadName) {
-    Start();
-  }
-  virtual ~GLHelperThread() {}
-
-  DISALLOW_COPY_AND_ASSIGN(GLHelperThread);
-};
-
-base::LazyInstance<GLHelperThread> g_gl_helper_thread =
-    LAZY_INSTANCE_INITIALIZER;
-
 class ScopedWebGLId {
  public:
   typedef void (WebKit::WebGraphicsContext3D::*DeleteFunc)(WebKit::WebGLId);
@@ -191,57 +171,6 @@ class ScopedTextureBinder : ScopedBinder<target> {
           &WebKit::WebGraphicsContext3D::bindTexture) {}
 };
 
-void ReadBackFramebuffer(
-    WebKit::WebGraphicsContext3D* context,
-    unsigned char* pixels,
-    gfx::Size size,
-    WebKit::WebGLId dst_texture,
-    bool* result) {
-  *result = false;
-  if (!context->makeContextCurrent())
-    return;
-  if (context->isContextLost())
-    return;
-  ScopedFramebuffer dst_framebuffer(context, context->createFramebuffer());
-  {
-    ScopedFramebufferBinder<GL_DRAW_FRAMEBUFFER> framebuffer_binder(
-        context, dst_framebuffer);
-    ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(
-        context, dst_texture);
-    context->framebufferTexture2D(GL_DRAW_FRAMEBUFFER,
-                                  GL_COLOR_ATTACHMENT0,
-                                  GL_TEXTURE_2D,
-                                  dst_texture,
-                                  0);
-  }
-  *result = context->readBackFramebuffer(
-        pixels,
-        4 * size.GetArea(),
-        static_cast<WebKit::WebGLId>(dst_framebuffer),
-        size.width(),
-        size.height());
-  context->flush();
-}
-
-void ReadBackFramebufferComplete(WebKit::WebGraphicsContext3D* context,
-                                 WebKit::WebGLId* dst_texture,
-                                 base::Callback<void(bool)> callback,
-                                 bool* result) {
-  callback.Run(*result);
-  if (*dst_texture != 0) {
-    context->deleteTexture(*dst_texture);
-    *dst_texture = 0;
-  }
-}
-
-void DeleteContext(WebKit::WebGraphicsContext3D* context) {
-  delete context;
-}
-
-void SignalWaitableEvent(base::WaitableEvent* event) {
-  event->Signal();
-}
-
 }  // namespace
 
 namespace content {
@@ -250,20 +179,15 @@ namespace content {
 class GLHelper::CopyTextureToImpl {
  public:
   CopyTextureToImpl(WebKit::WebGraphicsContext3D* context,
-                    WebKit::WebGraphicsContext3D* context_for_thread,
                     GLHelper* helper)
       : context_(context),
-        context_for_thread_(context_for_thread),
         helper_(helper),
         program_(context, context->createProgram()),
-        vertex_attributes_buffer_(context_, context_->createBuffer()),
-        dst_texture_(0) {
+        vertex_attributes_buffer_(context_, context_->createBuffer()) {
     InitBuffer();
     InitProgram();
   }
-  ~CopyTextureToImpl() {
-    DeleteContextForThread();
-  }
+  ~CopyTextureToImpl() {}
 
   void InitBuffer();
   void InitProgram();
@@ -273,21 +197,7 @@ class GLHelper::CopyTextureToImpl {
                      const gfx::Size& src_size,
                      const gfx::Size& dst_size,
                      unsigned char* out);
-
-  void AsyncCopyTextureTo(WebKit::WebGLId src_texture,
-                          const gfx::Size& src_size,
-                          const gfx::Size& dst_size,
-                          unsigned char* out,
-                          base::Callback<void(bool)> callback);
  private:
-  // Returns the id of a framebuffer that
-  WebKit::WebGLId ScaleTexture(WebKit::WebGLId src_texture,
-                               const gfx::Size& src_size,
-                               const gfx::Size& dst_size);
-
-  // Deletes the context for GLHelperThread.
-  void DeleteContextForThread();
-
   // Interleaved array of 2-dimentional vertex positions (x, y) and
   // 2-dimentional texture coordinates (s, t).
   static const WebKit::WGC3Dfloat kVertexAttributes[];
@@ -296,7 +206,6 @@ class GLHelper::CopyTextureToImpl {
   static const WebKit::WGC3Dchar kCopyFragmentShader[];
 
   WebKit::WebGraphicsContext3D* context_;
-  WebKit::WebGraphicsContext3D* context_for_thread_;
   GLHelper* helper_;
 
   // A program for copying a source texture into a destination texture.
@@ -310,8 +219,6 @@ class GLHelper::CopyTextureToImpl {
   WebKit::WGC3Dint texcoord_location_;
   // The location of the source texture in the program.
   WebKit::WGC3Dint texture_location_;
-  // The destination texture id. This is used only for the asynchronous version.
-  WebKit::WebGLId dst_texture_;
 };
 
 const WebKit::WGC3Dfloat GLHelper::CopyTextureToImpl::kVertexAttributes[] = {
@@ -374,21 +281,19 @@ void GLHelper::CopyTextureToImpl::InitProgram() {
 void GLHelper::CopyTextureToImpl::Detach() {
   program_.Detach();
   vertex_attributes_buffer_.Detach();
-  dst_texture_ = 0;
 }
 
-WebKit::WebGLId GLHelper::CopyTextureToImpl::ScaleTexture(
-    WebKit::WebGLId src_texture,
-    const gfx::Size& src_size,
-    const gfx::Size& dst_size) {
-  WebKit::WebGLId dst_texture = context_->createTexture();
+bool GLHelper::CopyTextureToImpl::CopyTextureTo(WebKit::WebGLId src_texture,
+                                                const gfx::Size& src_size,
+                                                const gfx::Size& dst_size,
+                                                unsigned char* out) {
+  ScopedFramebuffer dst_framebuffer(context_, context_->createFramebuffer());
+  ScopedTexture dst_texture(context_, context_->createTexture());
   {
-    ScopedFramebuffer dst_framebuffer(context_, context_->createFramebuffer());
     ScopedFramebufferBinder<GL_DRAW_FRAMEBUFFER> framebuffer_binder(
         context_, dst_framebuffer);
     {
-      ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(
-          context_, dst_texture);
+      ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(context_, dst_texture);
       context_->texImage2D(GL_TEXTURE_2D,
                            0,
                            GL_RGBA,
@@ -435,102 +340,22 @@ WebKit::WebGLId GLHelper::CopyTextureToImpl::ScaleTexture(
     // Conduct texture mapping by drawing a quad composed of two triangles.
     context_->drawArrays(GL_TRIANGLE_STRIP, 0, 4);
   }
-  return dst_texture;
-}
-
-void GLHelper::CopyTextureToImpl::DeleteContextForThread() {
-  if (!context_for_thread_)
-    return;
-
-  g_gl_helper_thread.Pointer()->message_loop_proxy()->PostTask(
-      FROM_HERE,
-      base::Bind(&DeleteContext,
-                 context_for_thread_));
-  context_for_thread_ = NULL;
-}
 
-bool GLHelper::CopyTextureToImpl::CopyTextureTo(
-    WebKit::WebGLId src_texture,
-    const gfx::Size& src_size,
-    const gfx::Size& dst_size,
-    unsigned char* out) {
-  ScopedTexture dst_texture(context_,
-                            ScaleTexture(src_texture, src_size, dst_size));
-  ScopedFramebuffer dst_framebuffer(context_, context_->createFramebuffer());
-  {
-    ScopedFramebufferBinder<GL_DRAW_FRAMEBUFFER> framebuffer_binder(
-        context_, dst_framebuffer);
-    ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(
-        context_, dst_framebuffer);
-    context_->framebufferTexture2D(GL_DRAW_FRAMEBUFFER,
-                                   GL_COLOR_ATTACHMENT0,
-                                   GL_TEXTURE_2D,
-                                   dst_texture,
-                                   0);
-  }
+  // TODO(mazda): Do this on another thread because this can block the UI
+  // thread for possibly a long time (http://crbug.com/118547).
   return context_->readBackFramebuffer(
       out,
-      4 * dst_size.GetArea(),
-      static_cast<WebKit::WebGLId>(dst_framebuffer),
+      4 * dst_size.width() * dst_size.height(),
+      dst_framebuffer,
       dst_size.width(),
       dst_size.height());
 }
 
-void GLHelper::CopyTextureToImpl::AsyncCopyTextureTo(
-    WebKit::WebGLId src_texture,
-    const gfx::Size& src_size,
-    const gfx::Size& dst_size,
-    unsigned char* out,
-    base::Callback<void(bool)> callback) {
-  if (!context_for_thread_) {
-    callback.Run(false);
-    return;
-  }
-
-  dst_texture_ = ScaleTexture(src_texture, src_size, dst_size);
-  context_->flush();
-  bool* result = new bool(false);
-  g_gl_helper_thread.Pointer()->message_loop_proxy()->PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&ReadBackFramebuffer,
-                 context_for_thread_,
-                 out,
-                 dst_size,
-                 dst_texture_,
-                 result),
-      base::Bind(&ReadBackFramebufferComplete,
-                 context_,
-                 &dst_texture_,
-                 callback,
-                 base::Owned(result)));
-}
-
-base::subtle::Atomic32 GLHelper::count_ = 0;
-
-GLHelper::GLHelper(WebKit::WebGraphicsContext3D* context,
-                   WebKit::WebGraphicsContext3D* context_for_thread)
-    : context_(context),
-      context_for_thread_(context_for_thread) {
-  base::subtle::NoBarrier_AtomicIncrement(&count_, 1);
+GLHelper::GLHelper(WebKit::WebGraphicsContext3D* context)
+    : context_(context) {
 }
 
 GLHelper::~GLHelper() {
-  DCHECK_NE(MessageLoop::current(),
-            g_gl_helper_thread.Pointer()->message_loop());
-  base::subtle::Atomic32 decremented_count =
-    base::subtle::NoBarrier_AtomicIncrement(&count_, -1);
-  if (decremented_count == 0) {
-    // When this is the last instance, we synchronize with the pending
-    // operations on GLHelperThread. Otherwise on shutdown we may kill the GPU
-    // process infrastructure (BrowserGpuChannelHostFactory) before they have
-    // a chance to complete, likely leading to a crash.
-    base::WaitableEvent event(false, false);
-    g_gl_helper_thread.Pointer()->message_loop_proxy()->PostTask(
-        FROM_HERE,
-        base::Bind(&SignalWaitableEvent,
-                   &event));
-    event.Wait();
-  }
 }
 
 WebKit::WebGraphicsContext3D* GLHelper::context() const {
@@ -548,33 +373,13 @@ bool GLHelper::CopyTextureTo(WebKit::WebGLId src_texture,
                              unsigned char* out) {
   // Lazily initialize |copy_texture_to_impl_|
   if (!copy_texture_to_impl_.get())
-    copy_texture_to_impl_.reset(new CopyTextureToImpl(context_,
-                                                      context_for_thread_,
-                                                      this));
-
-  return copy_texture_to_impl_->CopyTextureTo(
-      src_texture,
-      src_size,
-      dst_size,
-      out);
-}
+    copy_texture_to_impl_.reset(new CopyTextureToImpl(context_, this));
+
+  return copy_texture_to_impl_->CopyTextureTo(src_texture,
+                                              src_size,
+                                              dst_size,
+                                              out);
 
-void GLHelper::AsyncCopyTextureTo(WebKit::WebGLId src_texture,
-                                  const gfx::Size& src_size,
-                                  const gfx::Size& dst_size,
-                                  unsigned char* out,
-                                  const base::Callback<void(bool)>& callback) {
-  // Lazily initialize |copy_texture_to_impl_|
-  if (!copy_texture_to_impl_.get())
-    copy_texture_to_impl_.reset(new CopyTextureToImpl(context_,
-                                                      context_for_thread_,
-                                                      this));
-
-  copy_texture_to_impl_->AsyncCopyTextureTo(src_texture,
-                                            src_size,
-                                            dst_size,
-                                            out,
-                                            callback);
 }
 
 WebKit::WebGLId GLHelper::CompileShaderFromSource(
diff --git a/content/common/gpu/client/gl_helper.h b/content/common/gpu/client/gl_helper.h
index 771cad3..73e7949 100644
--- a/content/common/gpu/client/gl_helper.h
+++ b/content/common/gpu/client/gl_helper.h
@@ -6,9 +6,7 @@
 #define CONTENT_COMMON_GPU_CLIENT_GL_HELPER_H_
 #pragma once
 
-#include "base/atomicops.h"
 #include "base/basictypes.h"
-#include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebGraphicsContext3D.h"
 
@@ -22,8 +20,7 @@ namespace content {
 // interfaces.
 class GLHelper {
  public:
-  GLHelper(WebKit::WebGraphicsContext3D* context,
-           WebKit::WebGraphicsContext3D* context_for_thread);
+  GLHelper(WebKit::WebGraphicsContext3D* context);
   virtual ~GLHelper();
 
   WebKit::WebGraphicsContext3D* context() const;
@@ -38,14 +35,6 @@ class GLHelper {
                      const gfx::Size& dst_size,
                      unsigned char* out);
 
-  // Asynchronous version of CopyTextureTo. |callback| is invoked with the copy
-  // result when the copy operation has completed.
-  void AsyncCopyTextureTo(WebKit::WebGLId src_texture,
-                          const gfx::Size& src_size,
-                          const gfx::Size& dst_size,
-                          unsigned char* out,
-                          const base::Callback<void(bool)>& callback);
-
   // Returns the shader compiled from the source.
   WebKit::WebGLId CompileShaderFromSource(const WebKit::WGC3Dchar* source,
                                           WebKit::WGC3Denum type);
@@ -54,12 +43,8 @@ class GLHelper {
   class CopyTextureToImpl;
 
   WebKit::WebGraphicsContext3D* context_;
-  WebKit::WebGraphicsContext3D* context_for_thread_;
   scoped_ptr<CopyTextureToImpl> copy_texture_to_impl_;
 
-  // The number of all GLHelper instances.
-  static base::subtle::Atomic32 count_;
-
   DISALLOW_COPY_AND_ASSIGN(GLHelper);
 };
 
diff --git a/content/port/browser/render_widget_host_view_port.h b/content/port/browser/render_widget_host_view_port.h
index 55e06be..a45a214 100644
--- a/content/port/browser/render_widget_host_view_port.h
+++ b/content/port/browser/render_widget_host_view_port.h
@@ -6,7 +6,6 @@
 #define CONTENT_PORT_BROWSER_RENDER_WIDGET_HOST_VIEW_PORT_H_
 #pragma once
 
-#include "base/callback.h"
 #include "base/process_util.h"
 #include "base/string16.h"
 #include "content/common/content_export.h"
@@ -139,19 +138,11 @@ class CONTENT_EXPORT RenderWidgetHostViewPort : public RenderWidgetHostView {
   // Allocate a backing store for this view.
   virtual BackingStore* AllocBackingStore(const gfx::Size& size) = 0;
 
-  // DEPRECATED: Synchronous version of AsyncCopyFromCompositingSurface.
-  // This will be removed once all the caller have been chagned to use the
-  // asynchronous version.
-  virtual bool CopyFromCompositingSurface(const gfx::Size& size,
-                                          skia::PlatformCanvas* output) = 0;
-
-  // Asynchrnously copies the contents of the compositing surface into the given
+  // Copies the contents of the compositing surface into the given
   // (uninitialized) PlatformCanvas if any. Returns true on success, false
   // otherwise.
-  virtual void AsyncCopyFromCompositingSurface(
-      const gfx::Size& size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) = 0;
+  virtual bool CopyFromCompositingSurface(const gfx::Size& size,
+                                          skia::PlatformCanvas* output) = 0;
 
   // Called when accelerated compositing state changes.
   virtual void OnAcceleratedCompositingStateChange() = 0;
diff --git a/content/public/browser/render_widget_host.h b/content/public/browser/render_widget_host.h
index 1529069..2a5bf15 100644
--- a/content/public/browser/render_widget_host.h
+++ b/content/public/browser/render_widget_host.h
@@ -6,7 +6,6 @@
 #define CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_
 #pragma once
 
-#include "base/callback.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/keyboard_listener.h"
 #include "content/public/browser/native_web_keyboard_event.h"
@@ -171,19 +170,10 @@ class CONTENT_EXPORT RenderWidgetHost : public IPC::Channel::Sender {
 
   virtual void Blur() = 0;
 
-  // DEPRECATED: Synchronous version of AsyncCopyFromBackingSurface.
-  // This will be removed once all the caller have been changed to use the
-  // asynchronous version.
-  virtual bool CopyFromBackingStore(const gfx::Rect& src_rect,
-                                    const gfx::Size& accelerated_dest_size,
-                                    skia::PlatformCanvas* output) = 0;
-
   // Copies the given subset of the backing store into the given (uninitialized)
   // PlatformCanvas. If |src_rect| is empty, the whole contents is copied.
-  // |callback| is invoked with true on success, false otherwise.
-  // When accelerated compositing is active, the contents is copied
-  // asynchronously from the compositing surface, but when the backing store is
-  // available, the contents is copied synchronously because it's fast enough.
+  // Returns true on success, false otherwise. When accelerated compositing is
+  // active, the contents is copied from the compositing surface.
   // If non empty |accelerated_dest_size| is given and accelerated compositing
   // is active, the content is shrinked so that it fits in
   // |accelerated_dest_size|. If |accelerated_dest_size| is larger than the
@@ -192,11 +182,10 @@ class CONTENT_EXPORT RenderWidgetHost : public IPC::Channel::Sender {
   // NOTE: |src_rect| is not supported yet when accelerated compositing is
   // active (http://crbug.com/118571) and the whole content is always copied
   // regardless of |src_rect|.
-  virtual void AsyncCopyFromBackingStore(
-      const gfx::Rect& src_rect,
-      const gfx::Size& accelerated_dest_size,
-      skia::PlatformCanvas* output,
-      base::Callback<void(bool)> callback) = 0;
+  virtual bool CopyFromBackingStore(const gfx::Rect& src_rect,
+                                    const gfx::Size& accelerated_dest_size,
+                                    skia::PlatformCanvas* output) = 0;
+
 #if defined(TOOLKIT_GTK)
   // Paint the backing store into the target's |dest_rect|.
   virtual bool CopyFromBackingStoreToGtkWindow(const gfx::Rect& dest_rect,
diff --git a/ui/gfx/compositor/compositor.cc b/ui/gfx/compositor/compositor.cc
index 0a94054..965d1cb 100644
--- a/ui/gfx/compositor/compositor.cc
+++ b/ui/gfx/compositor/compositor.cc
@@ -77,26 +77,9 @@ bool DefaultContextFactory::Initialize() {
 
 WebKit::WebGraphicsContext3D* DefaultContextFactory::CreateContext(
     Compositor* compositor) {
-  return CreateContextCommon(compositor, false);
-}
-
-WebKit::WebGraphicsContext3D* DefaultContextFactory::CreateOffscreenContext(
-    Compositor* compositor) {
-  return CreateContextCommon(compositor, true);
-}
-
-void DefaultContextFactory::RemoveCompositor(Compositor* compositor) {
-}
-
-WebKit::WebGraphicsContext3D* DefaultContextFactory::CreateContextCommon(
-    Compositor* compositor,
-    bool offscreen) {
   WebKit::WebGraphicsContext3D::Attributes attrs;
   attrs.shareResources = true;
   WebKit::WebGraphicsContext3D* context =
-      offscreen ?
-      webkit::gpu::WebGraphicsContext3DInProcessImpl::CreateForWebView(
-          attrs, false) :
       webkit::gpu::WebGraphicsContext3DInProcessImpl::CreateForWindow(
           attrs, compositor->widget(), share_group_.get());
   CommandLine* command_line = CommandLine::ForCurrentProcess();
@@ -109,6 +92,9 @@ WebKit::WebGraphicsContext3D* DefaultContextFactory::CreateContextCommon(
   return context;
 }
 
+void DefaultContextFactory::RemoveCompositor(Compositor* compositor) {
+}
+
 Texture::Texture(bool flipped, const gfx::Size& size)
     : texture_id_(0),
       flipped_(flipped),
diff --git a/ui/gfx/compositor/compositor.h b/ui/gfx/compositor/compositor.h
index d8d75dc..1a2422a 100644
--- a/ui/gfx/compositor/compositor.h
+++ b/ui/gfx/compositor/compositor.h
@@ -54,11 +54,6 @@ class COMPOSITOR_EXPORT ContextFactory {
   virtual WebKit::WebGraphicsContext3D* CreateContext(
       Compositor* compositor) = 0;
 
-  // Creates a context for given compositor used for offscreen rendering. See
-  // the comments of CreateContext to know how per-compositor data is handled.
-  virtual WebKit::WebGraphicsContext3D* CreateOffscreenContext(
-      Compositor* compositor) = 0;
-
   // Destroys per-compositor data.
   virtual void RemoveCompositor(Compositor* compositor) = 0;
 };
@@ -72,8 +67,6 @@ class COMPOSITOR_EXPORT DefaultContextFactory : public ContextFactory {
   // ContextFactory implementation
   virtual WebKit::WebGraphicsContext3D* CreateContext(
       Compositor* compositor) OVERRIDE;
-  virtual WebKit::WebGraphicsContext3D* CreateOffscreenContext(
-      Compositor* compositor) OVERRIDE;
   virtual void RemoveCompositor(Compositor* compositor) OVERRIDE;
 
   bool Initialize();
@@ -83,10 +76,6 @@ class COMPOSITOR_EXPORT DefaultContextFactory : public ContextFactory {
   }
 
  private:
-  WebKit::WebGraphicsContext3D* CreateContextCommon(
-      Compositor* compositor,
-      bool offscreen);
-
   scoped_refptr<gfx::GLShareGroup> share_group_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultContextFactory);