PPAPI: Reduce string copying in SerializedVar.

ppapi/proxy/serialized_var_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ppapi/proxy/ppapi_proxy_test.h"
 
 #include "ppapi/proxy/serialized_var.h"
 
 namespace ppapi {
 namespace proxy {
@@ skipping 87 matching lines @@
       var_tracker().AddRefVar(plugin_string);
       EXPECT_EQ(2, var_tracker().GetRefCountForObject(plugin_string));
       EXPECT_EQ(0u, sink().message_count());
       *out_param.OutParam(plugin_dispatcher()) = plugin_string;
     }
 
     // The SerializedVar should have set the string value internally. Nothing in
     // the var tracker should have changed yet, and no messages should have been
     // sent.
     SerializedVarTestReader reader(sv);
-    EXPECT_EQ(kTestString, reader.GetString());
+    EXPECT_EQ(kTestString, *reader.GetTrackerStringPtr());
     EXPECT_EQ(2, var_tracker().GetRefCountForObject(plugin_string));
     EXPECT_EQ(0u, sink().message_count());
   }
   // The reference the string had initially should be gone, and the reference we
   // passed to the host should also be gone, so the string should be removed.
   EXPECT_EQ(-1, var_tracker().GetRefCountForObject(plugin_string));
   EXPECT_EQ(0u, sink().message_count());
 }
 
 // Tests receiving an argument and passing it back to the browser as an output
@@ skipping 212 matching lines @@
   }
 
   // When the ReturnValue object goes out of scope, it should have sent a
   // release message to the browser.
   EXPECT_EQ(-1, var_tracker().GetRefCountForObject(plugin_object));
   EXPECT_EQ(1u, sink().message_count());
 }
 
 }  // namespace proxy
 }  // namespace ppapi