cc: Remove legacy accelerated painting path

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index da2f4f6ed2f6ad3a20bec56b5bd8125fe2aa99c0..7d37920402c9b3e80b8600da33060c90572e7233 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -155,13 +155,6 @@ bool GLRenderer::Initialize() {
   std::set<std::string> extensions(extensions_list.begin(),
                                    extensions_list.end());
 
-  if (Settings().accelerate_painting &&
-      extensions.count("GL_EXT_texture_format_BGRA8888") &&
-      extensions.count("GL_EXT_read_format_bgra"))
-    capabilities_.using_accelerated_painting = true;
-  else
-    capabilities_.using_accelerated_painting = false;
-
   capabilities_.using_partial_swap =
       Settings().partial_swap_enabled &&
       extensions.count("GL_CHROMIUM_post_sub_buffer");