Quit the loop immediately upon animation complete

The task posed in the complete callback can be executed
under load if it waits for idle. Explicitly exit upon
animation complete instead.

Bug: None
Test: Test no longer fails under load
Change-Id: Ibef010506fd7a888615b7d2d304d0a04c826d00d
Reviewed-on: https://chromium-review.googlesource.com/c/1357668Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612956}

ash/wm/overview/window_selector_controller_unittest.cc

@@ -55,6 +55,8 @@ class TestShellObserver : public ShellObserver {
 
     EXPECT_EQ(UNKNOWN, starting_animation_state_);
     starting_animation_state_ = canceled ? CANCELED : COMPLETED;
+    if (run_loop_)
+      run_loop_->Quit();
   }
   void OnOverviewModeEndingAnimationComplete(bool canceled) override {
     if (!should_monitor_animation_state_)
@@ -62,6 +64,8 @@ class TestShellObserver : public ShellObserver {
 
     EXPECT_EQ(UNKNOWN, ending_animation_state_);
     ending_animation_state_ = canceled ? CANCELED : COMPLETED;
+    if (run_loop_)
+      run_loop_->Quit();
   }
 
   void Reset() {
@@ -70,13 +74,17 @@ class TestShellObserver : public ShellObserver {
   }
 
   void WaitForStartingAnimationComplete() {
-    while (starting_animation_state_ != COMPLETED)
-      base::RunLoop().RunUntilIdle();
+    while (starting_animation_state_ != COMPLETED) {
+      run_loop_ = std::make_unique<base::RunLoop>();
+      run_loop_->RunUntilIdle();
+    }
   }
 
   void WaitForEndingAnimationComplete() {
-    while (ending_animation_state_ != COMPLETED)
-      base::RunLoop().RunUntilIdle();
+    while (ending_animation_state_ != COMPLETED) {
+      run_loop_ = std::make_unique<base::RunLoop>();
+      run_loop_->RunUntilIdle();
+    }
   }
 
   bool is_ended() const { return ending_animation_state_ != UNKNOWN; }
@@ -106,6 +114,8 @@ class TestShellObserver : public ShellObserver {
   // AnimationComplete.
   bool should_monitor_animation_state_;
 
+  std::unique_ptr<base::RunLoop> run_loop_;
+
   DISALLOW_COPY_AND_ASSIGN(TestShellObserver);
 };