Ensure that pinch-zoom scrollbar animations trigger a draw

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 423462148be821a37fe373e7469c2bcdbbfe7b29..8662e1693b76c41bf0065f815b3b39ceb5a215b5 100644
--- a/cc/trees/layer_tree_host_unittest_animation.cc
+++ b/cc/trees/layer_tree_host_unittest_animation.cc
@@ -765,5 +765,57 @@ class LayerTreeHostAnimationTestCheckerboardDoesntStartAnimations
 MULTI_THREAD_TEST_F(
     LayerTreeHostAnimationTestCheckerboardDoesntStartAnimations);
 
+// Test that creating a pinch-zoom scrollbar animation leads to AnimateLayers
+// being called.
+class LayerTreeHostAnimationTestPinchZoomScrollbars
+    : public LayerTreeHostAnimationTest {
+ public:
+  LayerTreeHostAnimationTestPinchZoomScrollbars()
+      : root_layer_(ContentLayer::Create(&client_)),
+        started_times_(0) {}
+
+  virtual void InitializeSettings(LayerTreeSettings* settings) OVERRIDE {
+    settings->use_pinch_zoom_scrollbars = true;
+  }
+
+  virtual void BeginTest() OVERRIDE {
+    root_layer_->SetIsDrawable(true);
+    root_layer_->SetBounds(gfx::Size(100, 100));
+    layer_tree_host()->SetRootLayer(root_layer_);

[danakj, 2013/04/17 20:54:09]

Can you set up the layer tree in SetupTree() instead of BeginTest()? Then you'll
get a viewport of the right size and stuff. Just make sure you call
LayerTreeHostAnimationTest::SetupTree(); after you set the root layer so it can
set up the rest.

The page scale stuff can stay here.

[ajuma, 2013/04/18 18:42:51]

Done.

+    layer_tree_host()->SetPageScaleFactorAndLimits(0.5, 0.5, 0.9);

[danakj, 2013/04/17 20:54:09]

These are floats. 0.5f etc

[wjmaclean, 2013/04/17 20:56:54]

Minor nit: we generally would only have pinch zoom scrollbars if page scale > 1.
Typical values might be

SetPageScaleFactorAndLimits(1.xx, 1, 4); // Probably '2' is less preferable to
1.xx in terms of generality.

[danakj, 2013/04/17 21:01:03]

Oh, is this test actually triggering the scrollbars then, or is it testing
something else? Can you verify that it fails without your change?

[ajuma, 2013/04/18 18:42:51]

Done.

+    PostSetNeedsCommitToMainThread();
+  }
+
+  virtual void AnimateLayers(LayerTreeHostImpl* host_impl,
+                             base::TimeTicks monotonic_time) OVERRIDE {
+    if (host_impl->active_tree()->page_scale_factor() == 1.0)

[danakj, 2013/04/17 20:54:09]

1.f

[ajuma, 2013/04/18 18:42:51]

Done.

+      return;
+
+    if (started_times_ == 0) {

[danakj, 2013/04/17 20:54:09]

seems like a good spot for a switch?

[ajuma, 2013/04/18 18:42:51]

Done.

+      host_impl->active_tree()->DidBeginScroll();
+      started_times_++;
+      return;
+    }
+
+    if (started_times_ == 1) {
+      host_impl->active_tree()->DidEndScroll();
+      started_times_++;
+      return;
+    }
+
+    if (started_times_ == 2)
+      EndTest();
+  }
+
+  virtual void AfterTest() OVERRIDE {}
+
+ private:
+  FakeContentLayerClient client_;
+  scoped_refptr<ContentLayer> root_layer_;
+  int started_times_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostAnimationTestPinchZoomScrollbars);
+
 }  // namespace
 }  // namespace cc