Add initial CC support for scroll-blocks-on

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 55ffa7fb994122e462ab07fe5099fa0bef581e6c..19f87e2b5f54256abdf29087eaf02ee98649d993 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -54,6 +54,7 @@ LayerImpl::LayerImpl(LayerTreeImpl* tree_impl,
       should_scroll_on_main_thread_(false),
       have_wheel_event_handlers_(false),
       have_scroll_event_handlers_(false),
+      scroll_blocks_on_(ScrollBlocksOnNone),
       user_scrollable_horizontal_(true),
       user_scrollable_vertical_(true),
       stacking_order_changed_(false),
@@ -392,7 +393,8 @@ void LayerImpl::ApplySentScrollDeltasFromAbortedCommit() {
 
 InputHandler::ScrollStatus LayerImpl::TryScroll(
     const gfx::PointF& screen_space_point,
-    InputHandler::ScrollInputType type) const {
+    InputHandler::ScrollInputType type,
+    ScrollBlocksOn effective_block_mode) const {
   if (should_scroll_on_main_thread()) {
     TRACE_EVENT0("cc", "LayerImpl::TryScroll: Failed ShouldScrollOnMainThread");
     return InputHandler::ScrollOnMainThread;
@@ -430,7 +432,14 @@ InputHandler::ScrollStatus LayerImpl::TryScroll(
     }
   }
 
-  if (type == InputHandler::Wheel && have_wheel_event_handlers()) {
+  if (have_scroll_event_handlers() &&
+      effective_block_mode & ScrollBlocksOnScrollEvent) {
+    TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed ScrollEventHandlers");
+    return InputHandler::ScrollOnMainThread;
+  }
+
+  if (type == InputHandler::Wheel && have_wheel_event_handlers() &&
+      effective_block_mode & ScrollBlocksOnWheelEvent) {
     TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed WheelEventHandlers");
     return InputHandler::ScrollOnMainThread;
   }
@@ -487,6 +496,7 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer->SetShouldScrollOnMainThread(should_scroll_on_main_thread_);
   layer->SetHaveWheelEventHandlers(have_wheel_event_handlers_);
   layer->SetHaveScrollEventHandlers(have_scroll_event_handlers_);
+  layer->SetScrollBlocksOn(scroll_blocks_on_);
   layer->SetNonFastScrollableRegion(non_fast_scrollable_region_);
   layer->SetTouchEventHandlerRegion(touch_event_handler_region_);
   layer->SetContentsOpaque(contents_opaque_);
@@ -649,6 +659,17 @@ base::DictionaryValue* LayerImpl::LayerTreeAsJson() const {
     result->Set("TouchRegion", region.release());
   }
 
+  if (scroll_blocks_on_) {
+    list = new base::ListValue;
+    if (scroll_blocks_on_ & ScrollBlocksOnStartTouch)
+      list->AppendString("StartTouch");
+    if (scroll_blocks_on_ & ScrollBlocksOnWheelEvent)
+      list->AppendString("WheelEvent");
+    if (scroll_blocks_on_ & ScrollBlocksOnScrollEvent)
+      list->AppendString("ScrollEvent");
+    result->Set("ScrollBlocksOn", list);
+  }
+
   list = new base::ListValue;
   for (size_t i = 0; i < children_.size(); ++i)
     list->Append(children_[i]->LayerTreeAsJson());
@@ -1440,6 +1461,9 @@ void LayerImpl::AsValueInto(base::debug::TracedValue* state) const {
     non_fast_scrollable_region_.AsValueInto(state);
     state->EndArray();
   }
+  if (scroll_blocks_on_) {
+    state->SetInteger("scroll_blocks_on", scroll_blocks_on_);
+  }
 
   state->BeginArray("children");
   for (size_t i = 0; i < children_.size(); ++i) {