Refactor GL bindings so there is no global GLApi or DriverGL.

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 c4470e8163b9bcad02becb46d5487236d218cb2c..928a137458704b91441488ee0c6f6505040ef50f 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -4847,6 +4847,10 @@ void GLES2DecoderImpl::Destroy(bool have_context) {
     gpu_tracer_.reset();
   }
 
+  // Destroy the surface before the context, some surface destructors make GL
+  // calls.
+  surface_ = nullptr;

[jbauman, 2017/01/18 21:32:09]

This puts it in a pretty weird state where the underlying gl surface exists, but
only because it's bound to the context, so if we switch contexts after this
everything will break. Do you know which surfaces would cause this problem?

[Geoff Lang, 2017/01/19 15:40:06]

I did some investigating and it looks like the context doesn't hold any
references to the surface, they would both destruct separately.  The issue I was
dealing with was that both GLContextCGL and GLImageIOSurface make GL calls in
their destructors and if the context is destroyed before the surface then it
hits the NoContextGLApi.

+
   if (group_.get()) {
     group_->Destroy(this, have_context);
     group_ = NULL;