Determine mask UVs based on texture size

cc/layers/render_surface_impl.cc

Index: cc/layers/render_surface_impl.cc
diff --git a/cc/layers/render_surface_impl.cc b/cc/layers/render_surface_impl.cc
index a03fb006fec237bdeac7d59bbdc6e1c5fab60977..3f0c66e45485777f31c083263a2c0703e4c1c4f5 100644
--- a/cc/layers/render_surface_impl.cc
+++ b/cc/layers/render_surface_impl.cc
@@ -417,14 +417,11 @@ void RenderSurfaceImpl::AppendQuads(RenderPass* render_pass,
       return;
     }
     mask_layer->GetContentsResourceId(&mask_resource_id, &mask_texture_size);
-    gfx::SizeF unclipped_mask_target_size = gfx::ScaleSize(
-        gfx::SizeF(OwningEffectNode()->unscaled_mask_target_size),
-        surface_contents_scale.x(), surface_contents_scale.y());
     // Convert content_rect from target space to normalized space.
-    // Where unclipped_mask_target_size maps to gfx::Size(1, 1).
+    // Where mask_texture_size maps to gfx::Size(1, 1).
     mask_uv_rect = gfx::ScaleRect(gfx::RectF(content_rect()),
-                                  1.0f / unclipped_mask_target_size.width(),
-                                  1.0f / unclipped_mask_target_size.height());
+                                  1.0f / mask_texture_size.width(),
+                                  1.0f / mask_texture_size.height());
   }
 
   gfx::RectF tex_coord_rect(gfx::Rect(content_rect().size()));