Hook ANGLE_request_extension up to the passthrough cmd decoder.

ui/gl/gl_context.cc

Index: ui/gl/gl_context.cc
diff --git a/ui/gl/gl_context.cc b/ui/gl/gl_context.cc
index 3c1d61a0455e8b3b4fe90d68c5f0f2ad4ce1033e..d1ef28558144f1df375f4871f9a06a86abc9a45f 100644
--- a/ui/gl/gl_context.cc
+++ b/ui/gl/gl_context.cc
@@ -138,6 +138,12 @@ CurrentGL* GLContext::GetCurrentGL() {
   return current_gl_.get();
 }
 
+void GLContext::ReinitializeDynamicBindings() {
+  DCHECK(IsCurrent(nullptr));
+  dynamic_bindings_initialized_ = false;
+  InitializeDynamicBindings();
+}
+
 bool GLContext::HasExtension(const char* name) {
   std::string extensions = GetExtensions();
   extensions += " ";