Add GetProcAddress to OpenGL control interface

mojo/gles2/control_thunks_impl.cc

Index: mojo/gles2/control_thunks_impl.cc
diff --git a/mojo/gles2/control_thunks_impl.cc b/mojo/gles2/control_thunks_impl.cc
index 81cad387fbf4f51cd64553fea3d6262de09e9de0..071024ce7bff2a1e08b93197741ced821cde51f1 100644
--- a/mojo/gles2/control_thunks_impl.cc
+++ b/mojo/gles2/control_thunks_impl.cc
@@ -4,6 +4,7 @@
 
 #include "mojo/gles2/control_thunks_impl.h"
 
+#include "gpu/command_buffer/client/gles2_lib.h"
 #include "mojo/gles2/gles2_context.h"
 #include "mojo/public/cpp/system/message_pipe.h"
 
@@ -52,6 +53,10 @@ void ControlThunksImpl::SwapBuffers() {
   current_context_tls_.Get()->interface()->SwapBuffers();
 }
 
+MGLFunctionPointerType ControlThunksImpl::GetProcAddress(const char* name) {
+  return gles2::GetGLFunctionPointer(name);

[jamesr, 2015/09/21 19:38:50]

this will return things that the underlying library exposes but that we've
chosen not to expose through our thunks.  I don't think we want to do that -
it's too broad and it makes it hard to know what is exposed and what's not.
instead, we should only expose the functions that exist in the autogen headers
used when building the system.  In practice this means going through the autogen
tables to map names to exposed functions and return those. this could just be a
big chain of strncmp()s driven by the autogen header's macros for now and we can
make it a more efficient lookup later if we want (or not).

[Petr Hosek, 2015/09/22 20:06:54]

Done.

+}
+
 void* ControlThunksImpl::GetGLES2Interface(MGLContext context) {
   GLES2Context* client = reinterpret_cast<GLES2Context*>(context);
   DCHECK(client);