Enable TexStorage on Desktop GL lower than 4.2

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 58aa147c2a3e0a9dac15e9063ee17f7580049d46..1014e6df08fdd17fda640d9f290c3e5cd7d496f2 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -1034,7 +1034,7 @@ void FeatureInfo::InitializeFeatures() {
       (extensions.Contains("GL_EXT_texture_storage") ||
        extensions.Contains("GL_ARB_texture_storage") ||
        support_texture_storage_on_es3 ||
-       gl_version_info_->is_desktop_core_profile)) {
+       gl_version_info_->IsAtLeastGL(4, 2))) {

[piman, 2016/04/11 22:59:31]

I'm a bit confused... Is the goal to expose GL_EXT_texture_storage on the client
even when GL < 4.2? If so, it sounds like you would want to remove this check.
If not, I'm not sure how the client is supposed to know that calling TexStorage*
is allowed.

[Zhenyao Mo, 2016/04/11 23:17:19]

My bad.  I got my two different options mixed.

Option 1: implement the workaround.
Option 2: after I check various Mac devices, it seems ARB_texture_storage is
widely supported, so the workaround may not be necessary at all. We just need to
fix the gl bindings to make it work.

Let's go down option 2 for now, unless situations arise where a Mac driver
doesn't have the extension.

     feature_flags_.ext_texture_storage = true;
     AddExtensionString("GL_EXT_texture_storage");
     validators_.texture_parameter.AddValue(GL_TEXTURE_IMMUTABLE_FORMAT_EXT);