Hook ANGLE_request_extension up to the passthrough cmd decoder.

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
index 74c7a4a6d7522416bd5f4cc9e7af8ebacd7cec3e..2b8efd839c3bf9bca4bb0ce5fc2f80db655ea71c 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
@@ -2596,14 +2596,26 @@ error::Error GLES2DecoderPassthroughImpl::DoResizeCHROMIUM(GLuint width,
 
 error::Error GLES2DecoderPassthroughImpl::DoGetRequestableExtensionsCHROMIUM(
     const char** extensions) {
-  *extensions = "";
-  NOTIMPLEMENTED();
+  *extensions = reinterpret_cast<const char*>(
+      glGetString(GL_REQUESTABLE_EXTENSIONS_ANGLE));
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoRequestExtensionCHROMIUM(
     const char* extension) {
-  NOTIMPLEMENTED();
+  glRequestExtensionANGLE(extension);
+
+  // Make sure there are no pending GL errors before re-initializing feature
+  // info
+  FlushErrors();
+
+  // Make sure newly enabled extensions are exposed and usable.
+  context_->ReinitializeDynamicBindings();

[Zhenyao Mo, 2017/03/09 18:03:18]

This is potentially a perf concern for WebGL startup (they enable a bunch of
extensions at startup, each calling into this.

In theory, we can initialize all bindings unconditionally, and let validation
decide if a command is legitimate or not.

Could you at least add a TODO and maybe create a bug to look into this later?

[Geoff Lang, 2017/03/16 14:59:46]

Done, put a comment next to GLContext::ReinitializeDynamicBindings.

+  if (!feature_info_->Initialize(feature_info_->context_type(),
+                                 feature_info_->disallowed_features())) {
+    return error::kLostContext;
+  }
+
   return error::kNoError;
 }