Add initial CC support for scroll-blocks-on

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index face433a808db2c90727fb0b55880b4d3bddcf8e..b69cadb468ccdab72db33adb9e6400a130663197 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -71,6 +71,7 @@ Layer::Layer()
       force_render_surface_(false),
       transform_is_invertible_(true),
       has_render_surface_(false),
+      scroll_blocks_on_(ScrollBlocksOnNone),

[jdduke (slow), 2015/02/03 16:43:35]

I wonder if it's worth a static assert for ScrollBlocksOn values taking 3 bits
or less? 

[Rick Byers, 2015/02/05 04:35:53]

Sure, done.  I also updated my COMPILE_ASSERTs to match the static_assert
pattern I see elsewhere in cc/.

       background_color_(0),
       opacity_(1.f),
       blend_mode_(SkXfermode::kSrcOver_Mode),
@@ -758,6 +759,14 @@ void Layer::SetTouchEventHandlerRegion(const Region& region) {
   SetNeedsCommit();
 }
 
+void Layer::SetScrollBlocksOn(ScrollBlocksOn scroll_blocks_on) {
+  DCHECK(IsPropertyChangeAllowed());
+  if (scroll_blocks_on_ == scroll_blocks_on)
+    return;
+  scroll_blocks_on_ = scroll_blocks_on;
+  SetNeedsCommit();
+}
+
 void Layer::SetDrawCheckerboardForMissingTiles(bool checkerboard) {
   DCHECK(IsPropertyChangeAllowed());
   if (draw_checkerboard_for_missing_tiles_ == checkerboard)
@@ -911,6 +920,7 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
   layer->SetHaveScrollEventHandlers(have_scroll_event_handlers_);
   layer->SetNonFastScrollableRegion(non_fast_scrollable_region_);
   layer->SetTouchEventHandlerRegion(touch_event_handler_region_);
+  layer->SetScrollBlocksOn(scroll_blocks_on_);
   layer->SetContentsOpaque(contents_opaque_);
   if (!layer->OpacityIsAnimatingOnImplOnly() && !OpacityIsAnimating())
     layer->SetOpacity(opacity_);