cc: Scroll on main when possible incorrect hit testing hits scrollbar.

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index dac07a176c7d619da6e5e8e11ff5149209ed6bbe..8d18f5eabca27dddafae6d97038b2676e5d33a4e 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -938,6 +938,78 @@ TEST_F(LayerTreeHostImplTest, ShouldScrollOnMainThread) {
             status.main_thread_scrolling_reasons);
 }
 
+TEST_F(LayerTreeHostImplTest, ScrollWithOverlappingNonScrollableLayer) {
+  LayerTreeImpl* layer_tree_impl = host_impl_->active_tree();
+  gfx::Size content_size = gfx::Size(360, 600);
+  gfx::Size scroll_content_size = gfx::Size(345, 3800);
+  gfx::Size scrollbar_size = gfx::Size(15, 600);
+
+  host_impl_->SetViewportSize(content_size);
+  std::unique_ptr<LayerImpl> root = LayerImpl::Create(layer_tree_impl, 1);
+  root->SetBounds(content_size);
+  root->SetPosition(gfx::PointF());
+
+  std::unique_ptr<LayerImpl> clip = LayerImpl::Create(layer_tree_impl, 2);
+  clip->SetBounds(content_size);
+  clip->SetPosition(gfx::PointF());
+
+  std::unique_ptr<LayerImpl> scroll = LayerImpl::Create(layer_tree_impl, 3);
+  scroll->SetBounds(scroll_content_size);
+  scroll->SetScrollClipLayer(clip->id());
+  scroll->SetDrawsContent(true);
+
+  std::unique_ptr<SolidColorScrollbarLayerImpl> scrollbar =
+      SolidColorScrollbarLayerImpl::Create(layer_tree_impl, 4, VERTICAL, 10, 0,
+                                           false, true);
+  scrollbar->SetBounds(scrollbar_size);
+  scrollbar->SetPosition(gfx::PointF(345, 0));
+  scrollbar->SetScrollLayerId(scroll->id());
+  scrollbar->set_layer_or_descendant_is_drawn(true);
+  scrollbar->SetDrawsContent(true);
+
+  std::unique_ptr<LayerImpl> squash1 = LayerImpl::Create(layer_tree_impl, 5);
+  squash1->SetBounds(gfx::Size(140, 300));
+  squash1->SetPosition(gfx::PointF(220, 0));
+  squash1->SetDrawsContent(true);
+
+  std::unique_ptr<LayerImpl> squash2 = LayerImpl::Create(layer_tree_impl, 6);
+  squash2->SetBounds(gfx::Size(140, 300));
+  squash2->SetPosition(gfx::PointF(220, 300));
+  squash2->SetDrawsContent(true);
+
+  scroll->AddChild(std::move(squash2));
+  clip->AddChild(std::move(scroll));
+  clip->AddChild(std::move(scrollbar));
+  clip->AddChild(std::move(squash1));
+  root->AddChild(std::move(clip));
+
+  layer_tree_impl->SetRootLayer(std::move(root));
+  SetNeedsRebuildPropertyTrees();
+  RebuildPropertyTrees();
+  layer_tree_impl->DidBecomeActive();
+
+  // The point hits squash1 layer and also scroll layer, because scroll layer is
+  // not an ancestor of squash1 layer, we cannot scroll on impl thread.
+  InputHandler::ScrollStatus status = host_impl_->ScrollBegin(
+      BeginState(gfx::Point(230, 150)).get(), InputHandler::WHEEL);
+  EXPECT_EQ(InputHandler::SCROLL_UNKNOWN, status.thread);
+  EXPECT_EQ(MainThreadScrollingReason::kFailedHitTest,
+            status.main_thread_scrolling_reasons);
+
+  // The point hits squash1 layer and also scrollbar layer.
+  status = host_impl_->ScrollBegin(BeginState(gfx::Point(350, 150)).get(),
+                                   InputHandler::WHEEL);
+  EXPECT_EQ(InputHandler::SCROLL_UNKNOWN, status.thread);
+  EXPECT_EQ(MainThreadScrollingReason::kFailedHitTest,
+            status.main_thread_scrolling_reasons);
+
+  // The point hits squash2 layer and also scroll layer, because scroll layer is
+  // an ancestor of squash2 layer, we should scroll on impl.
+  status = host_impl_->ScrollBegin(BeginState(gfx::Point(230, 450)).get(),
+                                   InputHandler::WHEEL);
+  EXPECT_EQ(InputHandler::SCROLL_ON_IMPL_THREAD, status.thread);
+}
+
 TEST_F(LayerTreeHostImplTest, NonFastScrollableRegionBasic) {
   SetupScrollAndContentsLayers(gfx::Size(200, 200));
   host_impl_->SetViewportSize(gfx::Size(100, 100));