Verify that FetchEvent::m_request holds same-thread reference.

third_party/WebKit/Source/modules/serviceworkers/FetchEvent.h

Index: third_party/WebKit/Source/modules/serviceworkers/FetchEvent.h
diff --git a/third_party/WebKit/Source/modules/serviceworkers/FetchEvent.h b/third_party/WebKit/Source/modules/serviceworkers/FetchEvent.h
index cf6f25496022e7e0c5b92cdae2a211709234ad50..b2a15213ab408bd52e6e5fa90a667cbae06a91a0 100644
--- a/third_party/WebKit/Source/modules/serviceworkers/FetchEvent.h
+++ b/third_party/WebKit/Source/modules/serviceworkers/FetchEvent.h
@@ -74,7 +74,8 @@ class MODULES_EXPORT FetchEvent final : public ExtendableEvent {
 
  private:
   Member<RespondWithObserver> m_observer;
-  Member<Request> m_request;
+  // TODO(sof): remove once crbug.com/655926 has been diagnosed.
+  SameThreadCheckedMember<Request> m_request;
   Member<PreloadResponseProperty> m_preloadResponseProperty;
   String m_clientId;
   bool m_isReload;