Occlusion query feature is already in GL ES3.0 spec, not an extension.

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 dafa6caccd71a3c2772943f7ecc79212d51b26f4..61773e0d11e7f86f5c91e11706a5cc2c9afd4b2f 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -1044,6 +1044,8 @@ void FeatureInfo::InitializeFeatures() {
     }
   }
 
+  bool have_es3_occlusion_query =
+      gl_version_info_->IsAtLeastGLES(3, 0);
   bool have_ext_occlusion_query_boolean =
       extensions.Contains("GL_EXT_occlusion_query_boolean");
   bool have_arb_occlusion_query2 =
@@ -1051,10 +1053,15 @@ void FeatureInfo::InitializeFeatures() {
   bool have_arb_occlusion_query =
       extensions.Contains("GL_ARB_occlusion_query");
 
-  if (have_ext_occlusion_query_boolean ||
+  if (have_es3_occlusion_query ||
+      have_ext_occlusion_query_boolean ||
       have_arb_occlusion_query2 ||
       have_arb_occlusion_query) {
-    AddExtensionString("GL_EXT_occlusion_query_boolean");
+    if (have_ext_occlusion_query_boolean ||

[Zhenyao Mo, 2016/07/04 16:06:05]

You should use context_type_ is ES3 or WEBGL2 here.

Even if we are on top of ES3, extension names may still be included in the
EXTENSIONS string.

[xinghua.cao, 2016/07/05 14:21:23]

Zhenyao, sorry, I don't understand you clearly.
I think I did not change the code original logical flow. What I do is setting
"occlusion_query_boolean" to true only when context is ES3 and has not extension
names. And if we are on top of ES3 and extension names are included in the
EXTENSIONS string, AddExtensionString function will be called.
Do you mean that if context_type_ is ES3 or WebGL2, AddExtensionString cannot be
called? Could you give me more details, thank you.

[Zhenyao Mo, 2016/07/05 21:32:06]

The outside if conditions make sure we actually have the functionality in the
underlying driver, and the inside if conditions decide if we need to report the
extension string.  We only need to report the extension string in ES2 context. I
don't even think we need to report it if it's WebGL1 context. (Sorry my original
comment said the opposite thing)

+        have_arb_occlusion_query2 ||
+        have_arb_occlusion_query) {
+      AddExtensionString("GL_EXT_occlusion_query_boolean");
+    }
     feature_flags_.occlusion_query_boolean = true;
     feature_flags_.use_arb_occlusion_query2_for_occlusion_query_boolean =
         !have_ext_occlusion_query_boolean && have_arb_occlusion_query2;