Scroll on main if impl-hit testing isn't guaranteed to be correct

cc/trees/layer_tree_host_impl_unittest.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <cmath>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 5933 matching lines @@
 
     scoped_ptr<ScrollAndScaleSet> scroll_info =
         host_impl_->ProcessScrollDeltas();
 
     // The root should have scrolled.
     ASSERT_EQ(2u, scroll_info->scrolls.size());
     ExpectContains(*scroll_info.get(), root_scroll_id, gfx::Vector2d(0, 10));
   }
 }
 
+TEST_F(LayerTreeHostImplTest, ScrollUnknownNotOnAncestorChain) {
+  // If we ray cast a scroller that is not on the first layer's ancestor chain,
+  // we should return ScrollUnknown.
+  gfx::Size content_size(100, 100);
+  SetupScrollAndContentsLayers(content_size);
+
+  int scroll_layer_id = 2;
+  LayerImpl* scroll_layer =
+      host_impl_->active_tree()->LayerById(scroll_layer_id);
+  scroll_layer->SetDrawsContent(true);
+
+  int page_scale_layer_id = 5;
+  LayerImpl* page_scale_layer =
+      host_impl_->active_tree()->LayerById(page_scale_layer_id);
+
+  int occluder_layer_id = 6;
+  scoped_ptr<LayerImpl> occluder_layer =
+      LayerImpl::Create(host_impl_->active_tree(), occluder_layer_id);
+  occluder_layer->SetDrawsContent(true);
+  occluder_layer->SetBounds(content_size);
+  occluder_layer->SetContentBounds(content_size);
+  occluder_layer->SetPosition(gfx::PointF());
+  occluder_layer->SetAnchorPoint(gfx::PointF());
+
+  // The parent of the occluder is *above* the scroller.
+  page_scale_layer->AddChild(occluder_layer.Pass());
+
+  DrawFrame();
+
+  EXPECT_EQ(InputHandler::ScrollUnknown,
+            host_impl_->ScrollBegin(gfx::Point(), InputHandler::Wheel));
+}
+
+TEST_F(LayerTreeHostImplTest, ScrollUnknownScrollAncestorMismatch) {
+  // If we ray cast a scroller this is on the first layer's ancestor chain, but
+  // is not the first scroller we encounter when walking up from the layer, we
+  // should also return ScrollUnknown.
+  gfx::Size content_size(100, 100);
+  SetupScrollAndContentsLayers(content_size);
+
+  int scroll_layer_id = 2;
+  LayerImpl* scroll_layer =
+      host_impl_->active_tree()->LayerById(scroll_layer_id);
+  scroll_layer->SetDrawsContent(true);
+
+  int occluder_layer_id = 6;
+  scoped_ptr<LayerImpl> occluder_layer =
+      LayerImpl::Create(host_impl_->active_tree(), occluder_layer_id);
+  occluder_layer->SetDrawsContent(true);
+  occluder_layer->SetBounds(content_size);
+  occluder_layer->SetContentBounds(content_size);
+  occluder_layer->SetPosition(gfx::PointF());
+  occluder_layer->SetAnchorPoint(gfx::PointF());
+
+  int child_scroll_clip_layer_id = 7;
+  scoped_ptr<LayerImpl> child_scroll_clip =
+      LayerImpl::Create(host_impl_->active_tree(), child_scroll_clip_layer_id);
+
+  int child_scroll_layer_id = 8;
+  scoped_ptr<LayerImpl> child_scroll = CreateScrollableLayer(
+      child_scroll_layer_id, content_size, child_scroll_clip.get());
+
+  child_scroll->SetDrawsContent(false);
+
+  child_scroll->AddChild(occluder_layer.Pass());
+  scroll_layer->AddChild(child_scroll.Pass());
+
+  DrawFrame();
+
+  EXPECT_EQ(InputHandler::ScrollUnknown,
+            host_impl_->ScrollBegin(gfx::Point(), InputHandler::Wheel));
+}
+
 // Make sure LatencyInfo carried by LatencyInfoSwapPromise are passed
 // to CompositorFrameMetadata after SwapBuffers();
 TEST_F(LayerTreeHostImplTest, LatencyInfoPassedToCompositorFrameMetadata) {
   scoped_ptr<SolidColorLayerImpl> root =
       SolidColorLayerImpl::Create(host_impl_->active_tree(), 1);
   root->SetAnchorPoint(gfx::PointF());
   root->SetPosition(gfx::PointF());
   root->SetBounds(gfx::Size(10, 10));
   root->SetContentBounds(gfx::Size(10, 10));
   root->SetDrawsContent(true);
@@ skipping 308 matching lines @@
   EXPECT_EQ(host_impl_->global_tile_state().hard_memory_limit_in_bytes,
             300u * 1024u * 1024u);
   EXPECT_EQ(host_impl_->global_tile_state().soft_memory_limit_in_bytes,
             150u * 1024u * 1024u);
   EXPECT_EQ(host_impl_->global_tile_state().unused_memory_limit_in_bytes,
             75u * 1024u * 1024u);
 }
 
 }  // namespace
 }  // namespace cc