Ensure that pinch-zoom scrollbar animations trigger a draw

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 edf6722a07d8b7bddd8de1295148d541c0f956d2..da692e6961780360cdae99c72a137eae8c4ce694 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -276,6 +276,64 @@ class LayerTreeHostTestNoExtraCommitFromInvalidate : public LayerTreeHostTest {
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTestNoExtraCommitFromInvalidate);
 
+class LayerTreeHostTestNoExtraCommitFromScrollbarInvalidate
+    : public LayerTreeHostTest {
+ public:
+  LayerTreeHostTestNoExtraCommitFromScrollbarInvalidate()
+      : root_layer_(ContentLayer::Create(&client_)),
+        num_draws_(0) {}
+
+  virtual void SetupTree() OVERRIDE {
+    root_layer_->SetBounds(gfx::Size(10, 20));
+
+    bool paint_scrollbar = true;
+    bool has_thumb = false;
+    scrollbar_ = FakeScrollbarLayer::Create(paint_scrollbar,
+                                            has_thumb,
+                                            root_layer_->id());
+    scrollbar_->SetPosition(gfx::Point(0, 10));
+    scrollbar_->SetBounds(gfx::Size(10, 10));
+
+    root_layer_->AddChild(scrollbar_);
+
+    layer_tree_host()->SetRootLayer(root_layer_);
+    LayerTreeHostTest::SetupTree();
+  }
+
+  virtual void BeginTest() OVERRIDE {
+    PostSetNeedsCommitToMainThread();
+  }
+
+  virtual void DrawLayersOnThread(LayerTreeHostImpl* host_impl) OVERRIDE {
+    num_draws_++;
+    if (num_draws_ == 2)
+      EndTest();

[danakj, 2013/04/18 18:53:32]

Can you not tie this to the number of draws? You might get 2 draws for the first
commit. Just stick it in the DidCommit() method like the test above.

Looks like you won't need num_draws_ at all then.

[ajuma, 2013/04/18 18:59:08]

I tried this approach, but this wasn't enough to get a test that failed (for the
multi-thread case) without the fix to ScrollbarLayer, since the test would end
before the third commit arrived (but if we wait long enough, as the approach of
counting draws does, the third commit does arrive and cause the test to fail, as
we want).

[ajuma, 2013/04/18 19:21:25]

As discussed offline, changed this to use source_frame_number(), and made the
same change to the test above.

+  }
+
+  virtual void DidCommit() OVERRIDE {
+    switch (layer_tree_host()->commit_number()) {
+      case 1:
+        // This should cause a single commit.
+        scrollbar_->SetRasterScale(4.0f);
+        break;
+      default:
+        // No extra commits.
+        EXPECT_EQ(2, layer_tree_host()->commit_number());
+    }
+  }
+
+  virtual void AfterTest() OVERRIDE {}
+
+ private:
+  FakeContentLayerClient client_;
+  scoped_refptr<ContentLayer> root_layer_;

[danakj, 2013/04/18 18:53:32]

can you use FakeContentLayer instead? it does stuff like set up an AnchorPoint
you're expecting but not setting here.

[ajuma, 2013/04/18 19:21:25]

Done.

+  scoped_refptr<FakeScrollbarLayer> scrollbar_;
+  int num_draws_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTestNoExtraCommitFromScrollbarInvalidate);
+
 class LayerTreeHostTestCompositeAndReadback : public LayerTreeHostTest {
  public:
   LayerTreeHostTestCompositeAndReadback() : num_commits_(0) {}