cc : Enable LayerTreeHostTestGpuRasterDeviceSizeChanged test

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 00d1ee8c553a73259c90e0e7e98b44c4f05c10f0..2ed71f76c2dc413c8fc6041b981f39bf38941521 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -1514,6 +1514,7 @@ class LayerTreeHostTestGpuRasterDeviceSizeChanged : public LayerTreeHostTest {
   void DrawLayersOnThread(LayerTreeHostImpl* impl) override {
     if (num_draws_ < 2) {
       PostSetNeedsRedrawRectToMainThread(invalid_rect_);
+      PostSetNeedsCommitToMainThread();

[danakj, 2016/09/27 23:32:17]

Oh thanks for the investigation! I have a suggested fix, as it sounds like this
test is flaky because it might draw a diff number of times than commits, and in
those cases I don't think it ends up testing the right things, tho at least it
won't time out now.

What if we do:
- Increment num_draws_ in DidCommitAndDrawFrame.
- Move EndTest() to DidCommitAndDrawFrame.
- Move the PostSetNeedsRedrawRect to DidCommitAndDrawFrame.
- Remove DrawLayersOnThread.

Would that fix and also eliminate weird racing?

[jaydasika, 2016/09/27 23:42:58]

That + Adding PostSetNeedsCommitToMainThread() to CommitComplete() will work.

       num_draws_++;
     }
   }
@@ -1560,8 +1561,7 @@ class LayerTreeHostTestGpuRasterDeviceSizeChanged : public LayerTreeHostTest {
 
 // As there's no pending tree in single-threaded case, this test should run
 // only for multi-threaded case.
-// Disabled because its timing out flakily. crbug.com/598491
-// MULTI_THREAD_TEST_F(LayerTreeHostTestGpuRasterDeviceSizeChanged);
+MULTI_THREAD_TEST_F(LayerTreeHostTestGpuRasterDeviceSizeChanged);
 
 class LayerTreeHostTestNoExtraCommitFromInvalidate : public LayerTreeHostTest {
  public: