Make it possible to have 1 PpapiGlobals per thread. Update unit tests.

ppapi/proxy/serialized_var_unittest.cc

 // Copyright (c) 2011 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 97 matching lines @@
     EXPECT_EQ(kTestString, reader.GetString());
     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 out as an output parameter.
+// Tests receiving an argument and passing it back to the browser as an output
+// parameter.
 TEST_F(SerializedVarTest, PluginSerializedVarOutParam) {
   PP_Var host_object = MakeObjectVar(0x31337);
 
   // Start tracking this object in the plugin.
   PP_Var plugin_object = var_tracker().ReceiveObjectPassRef(
       host_object, plugin_dispatcher());
   EXPECT_EQ(1, var_tracker().GetRefCountForObject(plugin_object));
 
   {
     SerializedVar sv;
@@ skipping 201 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