Change SecurityOrigin from ThreadSafeRefCounted to RefCounted

SecurityOrigin should be thread-local and therefore RefCounted.

BUG=415865

Review URL: https://codereview.chromium.org/665893002

git-svn-id: svn://svn.chromium.org/blink/trunk@185270 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/weborigin/SecurityOrigin.h

@@ -38,7 +38,7 @@ namespace blink {
 class KURL;
 class SecurityOriginCache;
 
-class PLATFORM_EXPORT SecurityOrigin : public ThreadSafeRefCounted<SecurityOrigin> {
+class PLATFORM_EXPORT SecurityOrigin : public RefCounted<SecurityOrigin> {
 public:
     enum Policy {
         AlwaysDeny = 0,