Fix RenderWidgetHostViewAura as observer of CompositorVSyncManager

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 1c66023493c04e0418f29626a53b62edddb9e923..81245e51726beef1c660333520d7c3454072c769 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -67,6 +67,7 @@
 #include "ui/base/hit_test.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ui_base_types.h"
+#include "ui/compositor/compositor_vsync_manager.h"
 #include "ui/compositor/layer.h"
 #include "ui/events/event.h"
 #include "ui/events/event_utils.h"
@@ -3361,6 +3362,8 @@ RenderWidgetHostViewAura::~RenderWidgetHostViewAura() {
 #if defined(OS_WIN)
   legacy_render_widget_host_HWND_.reset(NULL);
 #endif
+
+  DCHECK(!vsync_manager_);
 }
 
 void RenderWidgetHostViewAura::UpdateCursorIfOverSelf() {
@@ -3531,8 +3534,11 @@ void RenderWidgetHostViewAura::AddedToRootWindow() {
 #endif
 
   ui::Compositor* compositor = GetCompositor();
-  if (compositor)
-    compositor->vsync_manager()->AddObserver(this);
+  if (compositor) {
+    DCHECK(!vsync_manager_);
+    vsync_manager_ = compositor->vsync_manager();
+    vsync_manager_->AddObserver(this);
+  }
 }
 
 void RenderWidgetHostViewAura::RemovingFromRootWindow() {
@@ -3557,11 +3563,8 @@ void RenderWidgetHostViewAura::RemovingFromRootWindow() {
   resize_lock_.reset();
   host_->WasResized();
 
-  if (compositor) {
-    if (compositor->HasObserver(this))
-      compositor->RemoveObserver(this);
-    compositor->vsync_manager()->RemoveObserver(this);
-  }
+  if (compositor && compositor->HasObserver(this))
+    compositor->RemoveObserver(this);
 
 #if defined(OS_WIN)
   // Update the legacy window's parent temporarily to the desktop window. It
@@ -3569,6 +3572,11 @@ void RenderWidgetHostViewAura::RemovingFromRootWindow() {
   if (legacy_render_widget_host_HWND_)
     legacy_render_widget_host_HWND_->UpdateParent(::GetDesktopWindow());
 #endif
+
+  if (vsync_manager_) {
+    vsync_manager_->RemoveObserver(this);
+    vsync_manager_ = NULL;
+  }
 }
 
 ui::Compositor* RenderWidgetHostViewAura::GetCompositor() const {