cc: Add initial GPU-to-GPU copy rasterizer implementation.

This adds a derived RasterWorkerPool class that use a smaller
resource pool for staging and initialize tile resources by
copying the contents of a staging resource to a tile resource
using CHROMIUM_copy_texture.

Zero-copy is still used by default when map-image rasterizer
is enabled using --enable-map-image. GPU-to-GPU copy
rasterizer is used when --disable-zero-copy switch is
provided in combination with --enable-map-image. This
zero-copy setting is also added to about:flags.

BUG=269808
TBR=sky

Review URL: https://codereview.chromium.org/236313006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@267455 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index fccaa70..5695270 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -216,7 +216,9 @@
 
   bool is_lcd_text_enabled() const { return is_lcd_text_enabled_; }
 
-  bool is_map_image_enabled() const { return is_map_image_enabled_; }
+  bool is_zero_copy_enabled() const { return is_zero_copy_enabled_; }
+
+  bool is_one_copy_enabled() const { return is_one_copy_enabled_; }
 
   AppCacheDispatcher* appcache_dispatcher() const {
     return appcache_dispatcher_.get();
@@ -543,7 +545,8 @@
   bool is_impl_side_painting_enabled_;
   bool is_low_res_tiling_enabled_;
   bool is_lcd_text_enabled_;
-  bool is_map_image_enabled_;
+  bool is_zero_copy_enabled_;
+  bool is_one_copy_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };