Turn on seamless cubemap by default on Desktop GL for ES3.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 7ecd8d5f47bf07b2f1410eb945e5d1295423c7b6..0f24ab9d40f4670793f8bd9fe9274267ff873f30 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2742,6 +2742,13 @@ bool GLES2DecoderImpl::Initialize(const scoped_refptr<gfx::GLSurface>& surface,
     frag_depth_explicitly_enabled_ = true;
     draw_buffers_explicitly_enabled_ = true;
     // TODO(zmo): Look into shader_texture_lod_explicitly_enabled_ situation.
+
+    // TEXTURE_CUBE_MAP_SEAMLESS is available on Desktop GL 3.2 or above.
+    // ES3 requires it to be always supported.
+    // We don't support ES3 on Desktop GL lower than 3.2.
+    if (!feature_info_->gl_version_info().BehavesLikeGLES()) {
+      glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS);
+    }

[piman, 2016/03/25 17:01:04]

Can you remove this? The code below will take care of it, right?

[Zhenyao Mo, 2016/03/25 17:17:29]

Ah, nasty.  I thought I deleted already.

   }
 
   state_.attrib_values.resize(group_->max_vertex_attribs());
@@ -3018,6 +3025,15 @@ bool GLES2DecoderImpl::Initialize(const scoped_refptr<gfx::GLSurface>& surface,
     glEnable(GL_PROGRAM_POINT_SIZE);
   }
 
+  // ES3 requires seamless cubemap. ES2 does not.
+  // However, when ES2 is implemented on top of DX11, seamless cubemap is
+  // always enabled and there is no way to disable it.
+  // Therefore, it seems OK to also always enable it on top of Desktop GL for
+  // both ES2 and ES3 contexts.
+  if (feature_info_->gl_version_info().IsAtLeastGL(3, 2)) {
+    glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS);
+  }
+
   has_robustness_extension_ =
       context->HasExtension("GL_ARB_robustness") ||
       context->HasExtension("GL_KHR_robustness") ||