Smooth Tab Switching on aura.

If there is no available front surface to display when switching to a tab, delay compositing until the next swap which gives us something
to display, or some timeout is reached instead.


BUG=126526
TEST=Manual


Review URL: https://chromiumcodereview.appspot.com/10543010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@141733 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/render_widget_host_view_aura.cc

@@ -287,10 +287,14 @@ RenderWidgetHost* RenderWidgetHostViewAura::GetRenderWidgetHost() const {
 
 void RenderWidgetHostViewAura::DidBecomeSelected() {
   host_->WasRestored();
+  if (!current_surface_ && host_->is_accelerated_compositing_active() &&
+      !released_front_lock_.get())
+    released_front_lock_ = window_->GetRootWindow()->GetCompositorLock();
 }
 
 void RenderWidgetHostViewAura::WasHidden() {
   host_->WasHidden();
+  released_front_lock_ = NULL;
 }
 
 void RenderWidgetHostViewAura::SetSize(const gfx::Size& size) {
@@ -506,6 +510,8 @@ void RenderWidgetHostViewAura::UpdateExternalTexture() {
       container->Update();
     window_->SetExternalTexture(container);
 
+    released_front_lock_ = NULL;
+
     if (!container) {
       resize_locks_.clear();
     } else {

content/browser/renderer_host/render_widget_host_view_aura.h

@@ -22,6 +22,10 @@
 #include "ui/gfx/rect.h"
 #include "webkit/glue/webcursor.h"
 
+namespace aura {
+class CompositorLock;
+}
+
 namespace content {
 class RenderWidgetHostImpl;
 class RenderWidgetHostView;
@@ -308,6 +312,9 @@ class RenderWidgetHostViewAura
   // These locks are the ones waiting for a frame to be drawn.
   std::vector<linked_ptr<ResizeLock> > locks_pending_draw_;
 
+  // This lock is for waiting for a front surface to become available to draw.
+  scoped_refptr<aura::CompositorLock> released_front_lock_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewAura);
 };