Make v8AtomicString take a StringView.

third_party/WebKit/Source/bindings/core/v8/WindowProxy.cpp

 /*
  * Copyright (C) 2008, 2009, 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 448 matching lines @@
         // SecurityOrigin::m_domain would have been modified.
         // m_domain is not used by SecurityOrigin::toString(), so we would end
         // up generating the same token that was already set.
         if (frameSecurityOrigin->domainWasSetInDOM() || frameSecurityToken.isEmpty() || frameSecurityToken == "null") {
             context->UseDefaultSecurityToken();
             return;
         }
         token = frameSecurityToken + token;
     }
 
-    CString utf8Token = token.utf8();

[esprehn, 2016/07/13 00:48:53]

Doing this meant we were allocating an extra temporary string plus we were doing
latin1 -> utf8 -> latin1 here for no reason.

     // NOTE: V8 does identity comparison in fast path, must use a symbol
     // as the security token.
-    context->SetSecurityToken(v8AtomicString(m_isolate, utf8Token.data(), utf8Token.length()));
+    context->SetSecurityToken(v8AtomicString(m_isolate, token));
 }
 
 void WindowProxy::updateDocument()
 {
     ASSERT(m_world->isMainWorld());
     if (!isGlobalInitialized())
         return;
     if (!isContextInitialized())
         return;
     updateActivityLogger();
@@ skipping 72 matching lines @@
 }
 
 void WindowProxy::updateSecurityOrigin(SecurityOrigin* origin)
 {
     if (!isContextInitialized())
         return;
     setSecurityToken(origin);
 }
 
 } // namespace blink