Free the resources used by a context group.

gpu/command_buffer/service/gpu_processor.cc

Index: gpu/command_buffer/service/gpu_processor.cc
===================================================================
--- gpu/command_buffer/service/gpu_processor.cc	(revision 51426)
+++ gpu/command_buffer/service/gpu_processor.cc	(working copy)
@@ -70,11 +70,15 @@
 }
 
 void GPUProcessor::DestroyCommon() {
+  bool have_context = false;
   if (decoder_.get()) {
+    have_context = decoder_->MakeCurrent();
     decoder_->Destroy();
     decoder_.reset();
   }
 
+  group_.Destroy(have_context);
+
   if (context_.get()) {
     context_->Destroy();
     context_.reset();