Made the CompositorAnimationObserver class usable

chrome/browser/chromeos/ui/accessibility_focus_ring_controller.cc

Index: chrome/browser/chromeos/ui/accessibility_focus_ring_controller.cc
diff --git a/chrome/browser/chromeos/ui/accessibility_focus_ring_controller.cc b/chrome/browser/chromeos/ui/accessibility_focus_ring_controller.cc
index 9b9aa4ea71372a5da88cc05789a6d2dd32c489f9..796c34df6fbcf9b45499f32885196df0578b6b1b 100644
--- a/chrome/browser/chromeos/ui/accessibility_focus_ring_controller.cc
+++ b/chrome/browser/chromeos/ui/accessibility_focus_ring_controller.cc
@@ -43,7 +43,7 @@ AccessibilityFocusRingController*
 }
 
 AccessibilityFocusRingController::AccessibilityFocusRingController()
-    : compositor_(NULL) {
+    : compositor_(nullptr) {
 }
 
 AccessibilityFocusRingController::~AccessibilityFocusRingController() {
@@ -80,7 +80,7 @@ void AccessibilityFocusRingController::Update() {
       layers_[0]->Set(rings_[0]);
       if (compositor_ && compositor_->HasAnimationObserver(this)) {
         compositor_->RemoveAnimationObserver(this);
-        compositor_ = NULL;
+        compositor_ = nullptr;
       }
       continue;
     }
@@ -309,7 +309,7 @@ void AccessibilityFocusRingController::OnAnimationStep(
   if (delta >= transition_time) {
     layers_[0]->Set(rings_[0]);
     compositor_->RemoveAnimationObserver(this);
-    compositor_ = NULL;
+    compositor_ = nullptr;
     return;
   }
 
@@ -322,4 +322,12 @@ void AccessibilityFocusRingController::OnAnimationStep(
       previous_rings_[0], rings_[0], fraction));
 }
 
+void AccessibilityFocusRingController::OnCompositingShuttingDown(
+    ui::Compositor* compositor) {

[xiyuan, 2015/06/01 18:06:35]

nit: DCHECK_EQ(compositor_, compositor);

+  if (compositor_) {
+    compositor_->RemoveAnimationObserver(this);
+  }
+  compositor_ = nullptr;
+}
+
 }  // namespace chromeos