Adding YUVA support for enabling Alpha Playback

cc/quads/yuv_video_draw_quad.cc

Index: cc/quads/yuv_video_draw_quad.cc
diff --git a/cc/quads/yuv_video_draw_quad.cc b/cc/quads/yuv_video_draw_quad.cc
index 7876861bd878578bf38d9e91a4d3db3fb4c9f024..d1eeeb7a9d83ab6e0109ac5c57e35c1e15c25ba9 100644
--- a/cc/quads/yuv_video_draw_quad.cc
+++ b/cc/quads/yuv_video_draw_quad.cc
@@ -16,20 +16,17 @@ scoped_ptr<YUVVideoDrawQuad> YUVVideoDrawQuad::Create() {
 }
 
 void YUVVideoDrawQuad::SetNew(const SharedQuadState* shared_quad_state,
-                              gfx::Rect rect,
-                              gfx::Rect opaque_rect,
-                              gfx::SizeF tex_scale,
-                              const VideoLayerImpl::FramePlane& y_plane,
-                              const VideoLayerImpl::FramePlane& u_plane,
-                              const VideoLayerImpl::FramePlane& v_plane) {
+                               gfx::Rect rect,
+                               gfx::Rect opaque_rect,
+                               gfx::SizeF tex_scale,
+                               const VideoLayerImpl::FramePlane* y_plane,
+                               const VideoLayerImpl::FramePlane* u_plane,
+                               const VideoLayerImpl::FramePlane* v_plane,
+                               const VideoLayerImpl::FramePlane* a_plane) {
   gfx::Rect visible_rect = rect;
   bool needs_blending = false;
-  DrawQuad::SetAll(shared_quad_state, DrawQuad::YUV_VIDEO_CONTENT, rect,
-                   opaque_rect, visible_rect, needs_blending);
-  this->tex_scale = tex_scale;
-  this->y_plane = y_plane;
-  this->u_plane = u_plane;
-  this->v_plane = v_plane;
+  SetAll(shared_quad_state, rect, opaque_rect, visible_rect, needs_blending,
+         tex_scale, y_plane, u_plane, v_plane, a_plane);
 }
 
 void YUVVideoDrawQuad::SetAll(const SharedQuadState* shared_quad_state,
@@ -38,15 +35,18 @@ void YUVVideoDrawQuad::SetAll(const SharedQuadState* shared_quad_state,
                               gfx::Rect visible_rect,
                               bool needs_blending,
                               gfx::SizeF tex_scale,
-                              const VideoLayerImpl::FramePlane& y_plane,
-                              const VideoLayerImpl::FramePlane& u_plane,
-                              const VideoLayerImpl::FramePlane& v_plane) {
+                              const VideoLayerImpl::FramePlane* y_plane,
+                              const VideoLayerImpl::FramePlane* u_plane,
+                              const VideoLayerImpl::FramePlane* v_plane,
+                              const VideoLayerImpl::FramePlane* a_plane) {
   DrawQuad::SetAll(shared_quad_state, DrawQuad::YUV_VIDEO_CONTENT, rect,
                    opaque_rect, visible_rect, needs_blending);
   this->tex_scale = tex_scale;
-  this->y_plane = y_plane;
-  this->u_plane = u_plane;
-  this->v_plane = v_plane;
+  this->y_plane = *y_plane;
+  this->u_plane = *u_plane;
+  this->v_plane = *v_plane;
+  if (a_plane)
+    this->a_plane = *a_plane;
 }
 
 void YUVVideoDrawQuad::IterateResources(
@@ -54,6 +54,8 @@ void YUVVideoDrawQuad::IterateResources(
   y_plane.resource_id = callback.Run(y_plane.resource_id);
   u_plane.resource_id = callback.Run(u_plane.resource_id);
   v_plane.resource_id = callback.Run(v_plane.resource_id);
+  if (a_plane.resource_id)
+    a_plane.resource_id = callback.Run(a_plane.resource_id);
 }
 
 const YUVVideoDrawQuad* YUVVideoDrawQuad::MaterialCast(