aura: fix hang when the content window is removed from the tree while a swap is pending

content/browser/renderer_host/render_widget_host_view_aura.cc

 // Copyright (c) 2012 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 "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "content/browser/renderer_host/backing_store_skia.h"
@@ skipping 94 matching lines @@
 // because clang doesn't like implementing multiple interfaces that have
 // methods with the same name. This object is owned by the
 // RenderWidgetHostViewAura.
 class RenderWidgetHostViewAura::WindowObserver : public aura::WindowObserver {
  public:
   WindowObserver(RenderWidgetHostViewAura* view) : view_(view) {}
   virtual ~WindowObserver() {}
 
     // Overridden from aura::WindowObserver:
   virtual void OnWindowRemovingFromRootWindow(aura::Window* window) OVERRIDE {
-    // TODO: It would be better to not use aura::RootWindow here
-    ui::Compositor* compositor = view_->GetCompositor();
-    if (compositor && compositor->HasObserver(view_))
-      compositor->RemoveObserver(view_);
+    view_->RemovingFromRootWindow();
   }
 
  private:
   RenderWidgetHostViewAura* view_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowObserver);
 };
 
 class RenderWidgetHostViewAura::ResizeLock :
     public base::SupportsWeakPtr<RenderWidgetHostViewAura::ResizeLock> {
@@ skipping 870 matching lines @@
 void RenderWidgetHostViewAura::OnActivated() {
 }
 
 void RenderWidgetHostViewAura::OnLostActive() {
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewAura, ui::CompositorDelegate implementation:
 
 void RenderWidgetHostViewAura::OnCompositingEnded(ui::Compositor* compositor) {
-  for (std::vector< base::Callback<void(void)> >::const_iterator
-      it = on_compositing_ended_callbacks_.begin();
-      it != on_compositing_ended_callbacks_.end(); ++it) {
-    it->Run();
-  }
-  on_compositing_ended_callbacks_.clear();
+  RunCompositingCallbacks();
   compositor->RemoveObserver(this);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewAura, ImageTransportFactoryObserver implementation:
 
 void RenderWidgetHostViewAura::OnLostResources(ui::Compositor* compositor) {
   image_transport_clients_.clear();
   current_surface_ = 0;
   UpdateExternalTexture();
@@ skipping 92 matching lines @@
   gfx::Rect rect = window_->bounds();
   int border_x = rect.width() * kMouseLockBorderPercentage / 100;
   int border_y = rect.height() * kMouseLockBorderPercentage / 100;
 
   return global_mouse_position_.x() < rect.x() + border_x ||
       global_mouse_position_.x() > rect.right() - border_x ||
       global_mouse_position_.y() < rect.y() + border_y ||
       global_mouse_position_.y() > rect.bottom() - border_y;
 }
 
+void RenderWidgetHostViewAura::RunCompositingCallbacks() {
+  for (std::vector< base::Callback<void(void)> >::const_iterator
+      it = on_compositing_ended_callbacks_.begin();
+      it != on_compositing_ended_callbacks_.end(); ++it) {
+    it->Run();
+  }
+  on_compositing_ended_callbacks_.clear();
+}
+
+void RenderWidgetHostViewAura::RemovingFromRootWindow() {
+  // We are about to disconnect ourselves from the compositor, we need to issue
+  // the callbacks now, because we won't get notified when the frame is done.
+  // TODO(piman): this might in theory cause a race where the GPU process starts
+  // drawing to the buffer we haven't yet displayed. This will only show for 1
+  // frame though, because we will reissue a new frame right away without that
+  // composited data.
+  RunCompositingCallbacks();
+  ui::Compositor* compositor = GetCompositor();
+  if (compositor && compositor->HasObserver(this))
+    compositor->RemoveObserver(this);
+}
+
 ui::Compositor* RenderWidgetHostViewAura::GetCompositor() {
   aura::RootWindow* root_window = window_->GetRootWindow();
   return root_window ? root_window->compositor() : NULL;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostView, public:
 
 // static
 RenderWidgetHostView* RenderWidgetHostView::CreateViewForWidget(
     RenderWidgetHost* widget) {
   return new RenderWidgetHostViewAura(widget);
 }
 
 // static
 void content::RenderWidgetHostViewPort::GetDefaultScreenInfo(
     WebKit::WebScreenInfo* results) {
   const gfx::Size size = gfx::Screen::GetPrimaryMonitorSize();
   results->rect = WebKit::WebRect(0, 0, size.width(), size.height());
   results->availableRect = results->rect;
   // TODO(derat): Don't hardcode this?
   results->depth = 24;
   results->depthPerComponent = 8;
   results->verticalDPI = 96;
   results->horizontalDPI = 96;
 }