Handle ui::Layer's visibility using cc::Layer's m_isDrawable flag

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index 119a1cfa868390103209691c432da434f32c665f..3b15433f6a8eb6533d2252b91d4e6c79b67116bb 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -438,7 +438,8 @@ void Layer::SetExternalTexture(Texture* texture) {
     }
     cc_layer_->setAnchorPoint(gfx::PointF());
     cc_layer_->setContentsOpaque(fills_bounds_opaquely_);
-    cc_layer_->setOpacity(visible_ ? opacity_ : 0.f);
+    cc_layer_->setOpacity(opacity_);
+    cc_layer_->setVisible(visible_);
     cc_layer_->setForceRenderSurface(force_render_surface_);
     cc_layer_->setIsDrawable(true);
     RecomputeTransform();
@@ -645,8 +646,7 @@ void Layer::SetOpacityImmediately(float opacity) {
   bool schedule_draw = (opacity != opacity_ && IsDrawn());
   opacity_ = opacity;
 
-  if (visible_)
-    cc_layer_->setOpacity(opacity);
+  cc_layer_->setOpacity(opacity);
   if (schedule_draw)
     ScheduleDraw();
 }
@@ -656,8 +656,7 @@ void Layer::SetVisibilityImmediately(bool visible) {
     return;
 
   visible_ = visible;
-  // TODO(piman): Expose a visibility flag on WebLayer.
-  cc_layer_->setOpacity(visible_ ? opacity_ : 0.f);
+  cc_layer_->setVisible(visible_);
 }
 
 void Layer::SetBrightnessImmediately(float brightness) {