gpu: Map glDiscardFramebufferEXT to glInvalidateFramebuffer

gpu/command_buffer/service/feature_info.cc

Index: gpu/command_buffer/service/feature_info.cc
diff --git a/gpu/command_buffer/service/feature_info.cc b/gpu/command_buffer/service/feature_info.cc
index 453b43d8a2b54c52befc50f7eda29d8436f1b43a..e9e427bba96a2b331e11e2ebfc5390dc9787b0e0 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -678,6 +678,11 @@ void FeatureInfo::AddFeatures(const CommandLine& command_line) {
     // TODO(dsinclair): Add AddExtensionString("GL_CHROMIUM_sampler_objects")
     // when available.
   }
+
+  if (is_es3) {
+    // DiscardFramebufferEXT is automatically bound to InvalidateFramebuffer.
+    AddExtensionString("GL_EXT_discard_framebuffer");
+  }
 }
 
 void FeatureInfo::AddExtensionString(const std::string& str) {