Make it possible to cancel commits following an animation

cc/trees/layer_tree_host_unittest_animation.cc

Index: cc/trees/layer_tree_host_unittest_animation.cc
diff --git a/cc/trees/layer_tree_host_unittest_animation.cc b/cc/trees/layer_tree_host_unittest_animation.cc
index 165d30b6df17b26288c49418b55905d652c04276..ee12e5cf596108d96d4bc4ff80faa8e120ebaa5d 100644
--- a/cc/trees/layer_tree_host_unittest_animation.cc
+++ b/cc/trees/layer_tree_host_unittest_animation.cc
@@ -783,6 +783,15 @@ class LayerTreeHostAnimationTestContinuousAnimate
         num_draw_layers_(0) {
   }
 
+  virtual void SetupTree() OVERRIDE {
+    LayerTreeHostAnimationTest::SetupTree();
+    // Create a fake content layer so we actually produce new content for every
+    // animation frame.
+    content_ = FakeContentLayer::Create(&client_);
+    content_->set_always_update_resources(true);
+    layer_tree_host()->root_layer()->AddChild(content_);
+  }
+
   virtual void BeginTest() OVERRIDE {
     PostSetNeedsCommitToMainThread();
   }
@@ -816,10 +825,118 @@ class LayerTreeHostAnimationTestContinuousAnimate
  private:
   int num_commit_complete_;
   int num_draw_layers_;
+  FakeContentLayerClient client_;
+  scoped_refptr<FakeContentLayer> content_;
 };
 
 MULTI_THREAD_TEST_F(LayerTreeHostAnimationTestContinuousAnimate);
 
+class LayerTreeHostAnimationTestCancelAnimateCommit
+    : public LayerTreeHostAnimationTest {
+ public:
+  LayerTreeHostAnimationTestCancelAnimateCommit() : num_animate_calls_(0) {}
+
+  virtual void BeginTest() OVERRIDE { PostSetNeedsCommitToMainThread(); }
+
+  virtual void Animate(base::TimeTicks) OVERRIDE {
+    // No-op animate will cancel the commit.
+    if (++num_animate_calls_ == 2) {
+      EndTest();
+      return;
+    }
+    layer_tree_host()->SetNeedsAnimate();
+  }
+
+  virtual void CommitCompleteOnThread(LayerTreeHostImpl* tree_impl) OVERRIDE {
+    if (num_animate_calls_ > 1)
+      FAIL() << "Commit should have been canceled.";
+  }
+
+  virtual void DrawLayersOnThread(LayerTreeHostImpl* impl) OVERRIDE {
+    if (num_animate_calls_ > 1)
+      FAIL() << "Draw should have been canceled.";
+  }
+
+  virtual void AfterTest() OVERRIDE { EXPECT_EQ(2, num_animate_calls_); }
+
+ private:
+  int num_animate_calls_;
+  FakeContentLayerClient client_;
+  scoped_refptr<FakeContentLayer> content_;
+};
+
+MULTI_THREAD_TEST_F(LayerTreeHostAnimationTestCancelAnimateCommit);
+
+class LayerTreeHostAnimationTestForceRedraw
+    : public LayerTreeHostAnimationTest {
+ public:
+  LayerTreeHostAnimationTestForceRedraw()
+      : num_animate_(0), num_draw_layers_(0) {}
+
+  virtual void BeginTest() OVERRIDE { PostSetNeedsCommitToMainThread(); }
+
+  virtual void Animate(base::TimeTicks) OVERRIDE {
+    if (++num_animate_ < 2)
+      layer_tree_host()->SetNeedsAnimate();
+  }
+
+  virtual void Layout() OVERRIDE {
+    layer_tree_host()->SetNextCommitForcesRedraw();
+  }
+
+  virtual void DrawLayersOnThread(LayerTreeHostImpl* impl) OVERRIDE {
+    if (++num_draw_layers_ == 2)
+      EndTest();
+  }
+
+  virtual void AfterTest() OVERRIDE {
+    // The first commit will always draw; make sure the second draw triggered
+    // by the animation was not cancelled.
+    EXPECT_EQ(2, num_draw_layers_);
+    EXPECT_EQ(2, num_animate_);
+  }
+
+ private:
+  int num_animate_;
+  int num_draw_layers_;
+};
+
+MULTI_THREAD_TEST_F(LayerTreeHostAnimationTestForceRedraw);
+
+class LayerTreeHostAnimationTestAnimateAfterSetNeedsCommit
+    : public LayerTreeHostAnimationTest {
+ public:
+  LayerTreeHostAnimationTestAnimateAfterSetNeedsCommit()
+      : num_animate_(0), num_draw_layers_(0) {}
+
+  virtual void BeginTest() OVERRIDE { PostSetNeedsCommitToMainThread(); }
+
+  virtual void Animate(base::TimeTicks) OVERRIDE {
+    if (++num_animate_ <= 2) {
+      layer_tree_host()->SetNeedsCommit();
+      layer_tree_host()->SetNeedsAnimate();
+    }
+  }
+
+  virtual void DrawLayersOnThread(LayerTreeHostImpl* impl) OVERRIDE {
+    if (++num_draw_layers_ == 2)
+      EndTest();
+  }
+
+  virtual void AfterTest() OVERRIDE {
+    // The first commit will always draw; make sure the second draw triggered
+    // by the SetNeedsCommit was not cancelled.
+    EXPECT_EQ(2, num_draw_layers_);
+    EXPECT_GE(num_animate_, 2);
+  }
+
+ private:
+  int num_animate_;
+  int num_draw_layers_;
+};
+
+MULTI_THREAD_TEST_F(LayerTreeHostAnimationTestAnimateAfterSetNeedsCommit);
+
 // Make sure the main thread can still execute animations when CanDraw() is not
 // true.
 class LayerTreeHostAnimationTestRunAnimationWhenNotCanDraw