Add better support for RGBA_4444 textures.

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 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 "content/renderer/gpu/render_widget_compositor.h"
 
 #include <limits>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 401 matching lines @@
     settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
   }
   settings.renderer_settings.highp_threshold_min = 2048;
   // Android WebView handles root layer flings itself.
   settings.ignore_root_layer_flings =
       synchronous_compositor_factory;
   // Memory policy on Android WebView does not depend on whether device is
   // low end, so always use default policy.
   bool use_low_memory_policy =
       base::SysInfo::IsLowEndDevice() && !synchronous_compositor_factory;
-  // RGBA_4444 textures are only enabled for low end devices
+  // RGBA_4444 textures are only enabled by default for low end devices
   // and are disabled for Android WebView as it doesn't support the format.
   settings.renderer_settings.use_rgba_4444_textures = use_low_memory_policy;
   if (use_low_memory_policy) {
     // On low-end we want to be very carefull about killing other
     // apps. So initially we use 50% more memory to avoid flickering
     // or raster-on-demand.
     settings.max_memory_for_prepaint_percentage = 67;
   } else {
     // On other devices we have increased memory excessively to avoid
     // raster-on-demand already, so now we reserve 50% _only_ to avoid
@@ skipping 22 matching lines @@
   settings.scrollbar_fade_duration_ms = 300;
 #endif
 
   if (cmd->HasSwitch(switches::kEnableLowResTiling))
     settings.create_low_res_tiling = true;
   if (cmd->HasSwitch(switches::kDisableLowResTiling))
     settings.create_low_res_tiling = false;
   if (cmd->HasSwitch(cc::switches::kEnableBeginFrameScheduling))
     settings.use_external_begin_frame_source = true;
 
+  settings.renderer_settings.use_rgba_4444_textures |=
+      cmd->HasSwitch(switches::kEnableRGBA4444Textures);
+  settings.renderer_settings.use_rgba_4444_textures &=
+      !cmd->HasSwitch(switches::kDisableRGBA4444Textures);
+
   if (widget_->for_oopif()) {
     // TODO(simonhong): Apply BeginFrame scheduling for OOPIF.
     // See crbug.com/471411.
     settings.use_external_begin_frame_source = false;
   }
 
   settings.max_staging_buffers = 32;
   // Use 1/4th of staging buffers on low-end devices.
   if (base::SysInfo::IsLowEndDevice())
     settings.max_staging_buffers /= 4;
@@ skipping 564 matching lines @@
     return;
   provider->ContextGL()->RateLimitOffscreenContextCHROMIUM();
 }
 
 void RenderWidgetCompositor::SetSurfaceIdNamespace(
     uint32_t surface_id_namespace) {
   layer_tree_host_->set_surface_id_namespace(surface_id_namespace);
 }
 
 }  // namespace content