aura: fast resizes for accelerated pages

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
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 3bb4d4dd479f1c96762573afd4f709ce81d353bb..a46418f7ee816a458cbe9ecfa8e019f71e5cdf3a 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -127,7 +127,8 @@ class RenderWidgetHostViewAura::ResizeLock :
  public:
   ResizeLock(aura::RootWindow* root_window, const gfx::Size new_size)
       : root_window_(root_window),
-        new_size_(new_size) {
+        new_size_(new_size),
+        compositor_lock_(root_window_->GetCompositorLock()) {
     root_window_->HoldMouseMoves();
 
     BrowserThread::PostDelayedTask(
@@ -141,9 +142,15 @@ class RenderWidgetHostViewAura::ResizeLock :
     CancelLock();
   }
 
+  void UnlockCompositor() {
+    compositor_lock_ = NULL;
+  }
+
   void CancelLock() {
-    if (root_window_)
-      root_window_->ReleaseMouseMoves();
+    if (!root_window_)
+      return;
+    UnlockCompositor();
+    root_window_->ReleaseMouseMoves();
     root_window_ = NULL;
   }
 
@@ -154,6 +161,7 @@ class RenderWidgetHostViewAura::ResizeLock :
  private:
   aura::RootWindow* root_window_;
   gfx::Size new_size_;
+  scoped_refptr<aura::CompositorLock> compositor_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(ResizeLock);
 };
@@ -419,7 +427,8 @@ void RenderWidgetHostViewAura::UpdateExternalTexture() {
     if (!container) {
       resize_locks_.clear();
     } else {
-      std::vector<linked_ptr<ResizeLock> >::iterator it = resize_locks_.begin();
+      typedef std::vector<linked_ptr<ResizeLock> > ResizeLockList;
+      ResizeLockList::iterator it = resize_locks_.begin();
       while (it != resize_locks_.end()) {
         if ((*it)->expected_size() == container->size())
           break;
@@ -434,6 +443,12 @@ void RenderWidgetHostViewAura::UpdateExternalTexture() {
           // draw a "good" frame.
           locks_pending_draw_.insert(
               locks_pending_draw_.begin(), resize_locks_.begin(), it);
+          // However since we got the size we were looking for, unlock the
+          // compositor.
+          for (ResizeLockList::iterator it2 = resize_locks_.begin();
+              it2 !=it; ++it2) {
+            it2->get()->UnlockCompositor();
+          }
           if (!compositor->HasObserver(this))
             compositor->AddObserver(this);
         }
@@ -462,12 +477,21 @@ void RenderWidgetHostViewAura::AcceleratedSurfaceBuffersSwapped(
         image_transport_clients_[params.surface_handle]->size();
     window_->SchedulePaintInRect(gfx::Rect(surface_size));
 
-    // Add sending an ACK to the list of things to do OnCompositingEnded
-    on_compositing_ended_callbacks_.push_back(
-        base::Bind(&RenderWidgetHostImpl::AcknowledgeSwapBuffers,
-                   params.route_id, gpu_host_id));
-    if (!compositor->HasObserver(this))
-      compositor->AddObserver(this);
+    if (!resize_locks_.empty() && !compositor->DrawPending()) {
+      // If we are waiting for the resize, fast-track the ACK.
+      // However only do so if we're not between the Draw() and the
+      // OnCompositingEnded(), because out-of-order execution in the GPU process
+      // might corrupt the "front buffer" for the currently issued frame.
+      RenderWidgetHostImpl::AcknowledgePostSubBuffer(
+          params.route_id, gpu_host_id);
+    } else {
+      // Add sending an ACK to the list of things to do OnCompositingEnded
+      on_compositing_ended_callbacks_.push_back(
+          base::Bind(&RenderWidgetHostImpl::AcknowledgeSwapBuffers,
+                     params.route_id, gpu_host_id));
+      if (!compositor->HasObserver(this))
+        compositor->AddObserver(this);
+    }
   }
 }
 
@@ -495,12 +519,21 @@ void RenderWidgetHostViewAura::AcceleratedSurfacePostSubBuffer(
         params.width,
         params.height));
 
-    // Add sending an ACK to the list of things to do OnCompositingEnded
-    on_compositing_ended_callbacks_.push_back(
-        base::Bind(&RenderWidgetHostImpl::AcknowledgePostSubBuffer,
-                   params.route_id, gpu_host_id));
-    if (!compositor->HasObserver(this))
-      compositor->AddObserver(this);
+    if (!resize_locks_.empty() && !compositor->DrawPending()) {
+      // If we are waiting for the resize, fast-track the ACK.
+      // However only do so if we're not between the Draw() and the
+      // OnCompositingEnded(), because out-of-order execution in the GPU process
+      // might corrupt the "front buffer" for the currently issued frame.
+      RenderWidgetHostImpl::AcknowledgePostSubBuffer(
+          params.route_id, gpu_host_id);
+    } else {
+      // Add sending an ACK to the list of things to do OnCompositingEnded
+      on_compositing_ended_callbacks_.push_back(
+          base::Bind(&RenderWidgetHostImpl::AcknowledgePostSubBuffer,
+                     params.route_id, gpu_host_id));
+      if (!compositor->HasObserver(this))
+        compositor->AddObserver(this);
+    }
   }
 }