mac: Fix bug where opacity is applied twice on RenderPassDrawQuads.

cc/output/gl_renderer.cc

 // Copyright 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/output/gl_renderer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 4024 matching lines @@
   GLfloat clip_rect[4] = {ca_layer_overlay->shared_state->clip_rect.x(),
                           ca_layer_overlay->shared_state->clip_rect.y(),
                           ca_layer_overlay->shared_state->clip_rect.width(),
                           ca_layer_overlay->shared_state->clip_rect.height()};
   GLint sorting_context_id = ca_layer_overlay->shared_state->sorting_context_id;
   SkMatrix44 transform = ca_layer_overlay->shared_state->transform;
   GLfloat gl_transform[16];
   transform.asColMajorf(gl_transform);
   unsigned filter = ca_layer_overlay->filter;
 
-  gl_->ScheduleCALayerSharedStateCHROMIUM(
-      ca_layer_overlay->shared_state->opacity, is_clipped, clip_rect,
-      sorting_context_id, gl_transform);
+  // The alpha has already been applied when copying the RPDQ to an IOSurface.
+  GLfloat alpha = 1;
+  gl_->ScheduleCALayerSharedStateCHROMIUM(alpha, is_clipped, clip_rect,
+                                          sorting_context_id, gl_transform);
   gl_->ScheduleCALayerCHROMIUM(
       texture_id, contents_rect, ca_layer_overlay->background_color,
       ca_layer_overlay->edge_aa_mask, bounds_rect, filter);
 }
 
 }  // namespace cc