gpu: Disable EXT_discard_framebuffer on ARM GPUs and expose it for pre-ES3

gpu/command_buffer/service/feature_info.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 "gpu/command_buffer/service/feature_info.h"
 
 #include <set>
 
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 667 matching lines @@
       !workarounds_.disable_async_readpixels) {
     feature_flags_.use_async_readpixels = true;
   }
 
   if (is_es3 || extensions.Contains("GL_ARB_sampler_objects")) {
     feature_flags_.enable_samplers = true;
     // TODO(dsinclair): Add AddExtensionString("GL_CHROMIUM_sampler_objects")
     // when available.
   }
 
-  if (is_es3) {
+  if ((is_es3 || extensions.Contains("GL_EXT_discard_framebuffer")) &&
+      !workarounds_.disable_ext_discard_framebuffer) {
     // DiscardFramebufferEXT is automatically bound to InvalidateFramebuffer.
     AddExtensionString("GL_EXT_discard_framebuffer");
   }
 }
 
 void FeatureInfo::AddExtensionString(const std::string& str) {
   if (extensions_.find(str) == std::string::npos) {
     extensions_ += (extensions_.empty() ? "" : " ") + str;
   }
 }
 
 FeatureInfo::~FeatureInfo() {
 }
 
 }  // namespace gles2
 }  // namespace gpu