cros: Fix unlock crash with multi-display

SessionController::RunUnlockAnimation expects the callback to be
invoked only once. SessionStateAnimatorImpl uses the callback per
animation per container. Mulit-display would have multiple containers
involved hence multiple animation and callbacks. The multiple
callback would cause a mojo CHECK failure. SessionStateAnimator
should only run the callback once after all animations finish.
The CL use a BarrierClosure to combine the animation callbacks.

BUG=712422
TEST=SessionStateAnimatiorImplContainersTest.AnimationCallbackOnMultiDisplay

Review-Url: https://codereview.chromium.org/2823343006
Cr-Commit-Position: refs/heads/master@{#465670}

ash/wm/session_state_animator.h

@@ -192,8 +192,8 @@ class ASH_EXPORT SessionStateAnimator {
                               AnimationSpeed speed) = 0;
 
   // Apply animation |type| to all containers included in |container_mask| with
-  // specified |speed| and call a |callback| at the end of the animation, if it
-  // is not null.
+  // specified |speed| and call a |callback| once at the end of the animations,
+  // if it is not null.
   virtual void StartAnimationWithCallback(int container_mask,
                                           AnimationType type,
                                           AnimationSpeed speed,

ash/wm/session_state_animator_impl.cc

@@ -9,6 +9,7 @@
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/shell.h"
 #include "ash/wm/wm_window_animations.h"
+#include "base/barrier_closure.h"
 #include "base/memory/ptr_util.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/window_event_dispatcher.h"
@@ -548,10 +549,12 @@ void SessionStateAnimatorImpl::StartAnimationWithCallback(
     base::Closure callback) {
   aura::Window::Windows containers;
   GetContainers(container_mask, &containers);
+  base::Closure animation_done_closure =
+      base::BarrierClosure(containers.size(), callback);
   for (aura::Window::Windows::const_iterator it = containers.begin();
        it != containers.end(); ++it) {
     ui::LayerAnimationObserver* observer =
-        new CallbackAnimationObserver(callback);
+        new CallbackAnimationObserver(animation_done_closure);
     RunAnimationForWindow(*it, type, speed, observer);
   }
 }

ash/wm/session_state_animator_impl_unittest.cc

@@ -2,11 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "ash/wm/session_state_animator_impl.h"
+
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "ash/wm/session_state_animator.h"
-#include "ash/wm/session_state_animator_impl.h"
+#include "base/bind.h"
+#include "base/run_loop.h"
 #include "ui/aura/client/aura_constants.h"
 
 typedef ash::test::AshTestBase SessionStateAnimatiorImplContainersTest;
@@ -80,4 +83,22 @@ TEST_F(SessionStateAnimatiorImplContainersTest, ContainersHaveIdTest) {
   EXPECT_TRUE(containers.empty());
 }
 
+// Test that SessionStateAnimatorImpl invokes the callback only once on
+// multi-display env, where it needs to run multiple animations on multiple
+// containers. See http://crbug.com/712422 for details.
+TEST_F(SessionStateAnimatiorImplContainersTest,
+       AnimationCallbackOnMultiDisplay) {
+  UpdateDisplay("200x200,400x400");
+
+  int callback_count = 0;
+  SessionStateAnimatorImpl animator;
+  animator.StartAnimationWithCallback(
+      SessionStateAnimator::LOCK_SCREEN_CONTAINERS,
+      SessionStateAnimator::ANIMATION_LIFT,
+      SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE,
+      base::Bind([](int* count) { ++(*count); }, &callback_count));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1, callback_count);
+}
+
 }  // namespace ash