Ensure LayerTreeHostImpl's current frame time is updated every frame

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index 3426d41fe446a15f5982801e99a5df4d09896e65..d471b069f7d2ffba6c05dc1750db023de80fd506 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -626,6 +626,52 @@ class LayerTreeHostTestCommit : public LayerTreeHostTest {
 
 MULTI_THREAD_TEST_F(LayerTreeHostTestCommit);
 
+// This test verifies that LayerTreeHostImpl's current frame time gets
+// updated in consecutive frames, even when it doesn't draw due to tree
+// activation failure.
+class LayerTreeHostTestFrameTimeUpdates : public LayerTreeHostTest {
+ public:
+  LayerTreeHostTestFrameTimeUpdates() : frame_(0) {}
+
+  virtual void BeginTest() OVERRIDE {
+    layer_tree_host()->SetViewportSize(gfx::Size(20, 20));
+    layer_tree_host()->set_background_color(SK_ColorGRAY);
+
+    PostSetNeedsCommitToMainThread();
+  }
+
+  virtual void DrawLayersOnThread(LayerTreeHostImpl* impl) OVERRIDE {
+    if (frame_ >= 1) {
+      EXPECT_NE(first_frame_time_, impl->CurrentFrameTimeTicks());
+      EndTest();
+      return;
+    }
+
+    EXPECT_FALSE(impl->settings().impl_side_painting);
+    frame_ = 1;

[danakj, 2013/05/16 15:37:18]

I think you can just EndTest() here, as this test is really meant for testing
activation.

Instead, could you add a second test that verifies that when we do draw a frame,
the frame time changes as well? That should cover both impl and non-impl paint.

[ajuma, 2013/05/16 17:24:34]

Done.
Done.

+    first_frame_time_ = impl->CurrentFrameTimeTicks();
+    impl->SetNeedsRedraw();
+  }
+
+  virtual bool CanActivatePendingTree(LayerTreeHostImpl* impl) OVERRIDE {
+    frame_++;
+    if (frame_ == 1) {
+      first_frame_time_ = impl->CurrentFrameTimeTicks();
+      return false;
+    }
+
+    return true;
+  }
+
+  virtual void AfterTest() OVERRIDE {}
+
+ private:
+  int frame_;
+  base::TimeTicks first_frame_time_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTestFrameTimeUpdates);
+
 // Verifies that StartPageScaleAnimation events propagate correctly
 // from LayerTreeHost to LayerTreeHostImpl in the MT compositor.
 class LayerTreeHostTestStartPageScaleAnimation : public LayerTreeHostTest {