Expose GL_CHROMIUM_compressed_texture_etc when ANGLE supports it.

ANGLE now exposes this extension under the same conditions as Chrome: on top
of a native ES driver.

BUG=angleproject:1552

Change-Id: I6552e51bccd5ece43b7405b26d63127283a90c46
Reviewed-on: https://chromium-review.googlesource.com/c/1342497Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609713}

gpu/command_buffer/service/feature_info.cc

@@ -1029,10 +1029,11 @@ void FeatureInfo::InitializeFeatures() {
     validators_.texture_internal_format_storage.AddValue(GL_ETC1_RGB8_OES);
   }
 
-  // TODO(kainino): Once we have a way to query whether ANGLE is exposing
-  // native support for ETC2 textures, require that here.
-  // http://anglebug.com/1552
-  if (gl_version_info_->is_es3 && !gl_version_info_->is_angle) {
+  // Expose GL_CHROMIUM_compressed_texture_etc when ANGLE exposes it directly or
+  // running on top of a non-ANGLE ES driver. We assume that this implies native
+  // support of these formats.
+  if (gfx::HasExtension(extensions, "GL_CHROMIUM_compressed_texture_etc") ||
+      (gl_version_info_->is_es3 && !gl_version_info_->is_angle)) {
     AddExtensionString("GL_CHROMIUM_compressed_texture_etc");
     validators_.UpdateETCCompressedTextureFormats();
   }

third_party/blink/renderer/modules/webgl/webgl_compressed_texture_etc.cc

@@ -11,6 +11,8 @@ namespace blink {
 WebGLCompressedTextureETC::WebGLCompressedTextureETC(
     WebGLRenderingContextBase* context)
     : WebGLExtension(context) {
+  context->ExtensionsUtil()->EnsureExtensionEnabled(
+      "GL_CHROMIUM_compressed_texture_etc");
   context->AddCompressedTextureFormat(GL_COMPRESSED_R11_EAC);
   context->AddCompressedTextureFormat(GL_COMPRESSED_SIGNED_R11_EAC);
   context->AddCompressedTextureFormat(GL_COMPRESSED_RGB8_ETC2);