Fix a crash in mus::GpuService

base/threading/thread_restrictions.h

Index: base/threading/thread_restrictions.h
diff --git a/base/threading/thread_restrictions.h b/base/threading/thread_restrictions.h
index e916ecc6f3b954e08127e55c5d442b12895f0866..a8d784dcfb07b9fd6b8dc2dd79bc909e2e77f180 100644
--- a/base/threading/thread_restrictions.h
+++ b/base/threading/thread_restrictions.h
@@ -64,6 +64,7 @@ class MessagePumpMojo;
 namespace mus {
 class CommandBufferClientImpl;
 class CommandBufferLocal;
+class GpuService;
 class GpuState;
 }
 namespace net {
@@ -213,6 +214,7 @@ class BASE_EXPORT ThreadRestrictions {
   friend class mojo::common::MessagePumpMojo;
   friend class mus::CommandBufferClientImpl;
   friend class mus::CommandBufferLocal;
+  friend class mus::GpuService;                   // http://crbug.com/620058
   friend class mus::GpuState;
 
   // END ALLOWED USAGE.