cc: Enable composited border-radius scrolling.

cc/layers/solid_color_layer_impl.cc

Index: cc/layers/solid_color_layer_impl.cc
diff --git a/cc/layers/solid_color_layer_impl.cc b/cc/layers/solid_color_layer_impl.cc
index c5b7574ccee75d9668ba91352810537a98116766..a85b8406d4005cee3e6ba727f922c87160c5162c 100644
--- a/cc/layers/solid_color_layer_impl.cc
+++ b/cc/layers/solid_color_layer_impl.cc
@@ -33,11 +33,13 @@ void SolidColorLayerImpl::AppendSolidQuads(
     SharedQuadState* shared_quad_state,
     const gfx::Rect& visible_layer_rect,
     SkColor color,
-    AppendQuadsData* append_quads_data) {
+    AppendQuadsData* append_quads_data,
+    Layer::LayerMaskType mask_type) {
   float alpha =
       (SkColorGetA(color) * (1.0f / 255.0f)) * shared_quad_state->opacity;
   DCHECK_EQ(SkBlendMode::kSrcOver, shared_quad_state->blend_mode);
-  if (alpha < std::numeric_limits<float>::epsilon())
+  if (alpha < std::numeric_limits<float>::epsilon() &&
+      mask_type != Layer::LayerMaskType::MULTI_TEXTURE_MASK)

[enne (OOO), 2017/05/12 17:51:33]

Why must these noop solid color quads not be skipped for multi texture masks?

[sunxd, 2017/05/15 17:57:36]

It was because mask layer's opacity is not calculated. I reverted the change
here and add the computation code.

     return;
   // We create a series of smaller quads instead of just one large one so that
   // the culler can reduce the total pixels drawn.
@@ -81,7 +83,7 @@ void SolidColorLayerImpl::AppendQuads(
   // |bounds()| here.
   AppendSolidQuads(render_pass, draw_properties().occlusion_in_content_space,
                    shared_quad_state, gfx::Rect(bounds()), background_color(),
-                   append_quads_data);
+                   append_quads_data, Layer::LayerMaskType::NOT_MASK);
 }
 
 const char* SolidColorLayerImpl::LayerTypeAsString() const {