aura: apply brightness filter last to improve perf

ui/compositor/layer.cc

 // Copyright (c) 2012 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 "ui/compositor/layer.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 60 matching lines @@
       compositor_(NULL),
       parent_(NULL),
       visible_(true),
       force_render_surface_(false),
       fills_bounds_opaquely_(true),
       layer_updated_externally_(false),
       opacity_(1.0f),
       background_blur_radius_(0),
       layer_saturation_(0.0f),
       layer_brightness_(0.0f),
+      layer_grayscale_(0.0f),
       layer_inverted_(false),
       layer_mask_(NULL),
       layer_mask_back_link_(NULL),
       delegate_(NULL),
       scale_content_(true),
       device_scale_factor_(1.0f) {
   CreateWebLayer();
 }
 
 Layer::~Layer() {
@@ skipping 190 matching lines @@
   if (layer_mask)
     layer_mask->layer_mask_back_link_ = this;
 }
 
 void Layer::SetLayerFilters() {
   WebKit::WebFilterOperations filters;
   if (layer_saturation_) {
     filters.append(WebKit::WebFilterOperation::createSaturateFilter(
         layer_saturation_));
   }
-  if (layer_brightness_) {
-    filters.append(WebKit::WebFilterOperation::createBrightnessFilter(
-        layer_brightness_));
-  }
   if (layer_grayscale_) {
     filters.append(WebKit::WebFilterOperation::createGrayscaleFilter(
         layer_grayscale_));
   }
   if (layer_inverted_)
     filters.append(WebKit::WebFilterOperation::createInvertFilter(1.0));
+  // Brightness goes last, because the resulting colors neeed clamping, which
+  // cause further color matrix filters to be applied separately. In this order,
+  // they all can be combined in a single pass.
+  if (layer_brightness_) {
+    filters.append(WebKit::WebFilterOperation::createBrightnessFilter(
+        layer_brightness_));
+  }
 
   web_layer_.setFilters(filters);
 }
 
 float Layer::GetTargetOpacity() const {
   if (animator_.get() && animator_->IsAnimatingProperty(
       LayerAnimationElement::OPACITY))
     return animator_->GetTargetOpacity();
   return opacity_;
 }
@@ skipping 454 matching lines @@
     return;
   unsigned int color = 0xFF000000;
   color |= web_layer_is_accelerated_ ? 0x0000FF00 : 0x00FF0000;
   bool opaque = fills_bounds_opaquely_ && (GetCombinedOpacity() == 1.f);
   if (!opaque)
     color |= 0xFF;
   web_layer_.setDebugBorderColor(color);
 }
 
 }  // namespace ui