Free the resources used by a context group.

gpu/command_buffer/service/buffer_manager.h

Index: gpu/command_buffer/service/buffer_manager.h
===================================================================
--- gpu/command_buffer/service/buffer_manager.h	(revision 51426)
+++ gpu/command_buffer/service/buffer_manager.h	(working copy)
@@ -143,7 +143,11 @@
   BufferManager()
       : allow_buffers_on_multiple_targets_(false) {
   }
+  ~BufferManager();
 
+  // Must call before destruction.
+  void Destroy(bool have_context);
+
   // Creates a BufferInfo for the given buffer.
   void CreateBufferInfo(GLuint client_id, GLuint service_id);