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

ppapi/shared_impl/proxy_lock.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/shared_impl/proxy_lock.h"
 
 #include "base/synchronization/lock.h"
+#include "ppapi/shared_impl/ppapi_globals.h"
 
 namespace ppapi {
 
-base::Lock* ProxyLock::lock_ = NULL;
-
 // static
 void ProxyLock::Acquire() {
-  if (lock_)
-    lock_->Acquire();
+  base::Lock* lock(PpapiGlobals::Get()->GetProxyLock());
+  if (lock)
+    lock->Acquire();
 }
 
 // static
 void ProxyLock::Release() {
-  if (lock_)
-    lock_->Release();
-}
-
-// static
-void ProxyLock::Set(base::Lock* lock) {
-  lock_ = lock;
-}
-
-// static
-void ProxyLock::Reset() {
-  Set(NULL);
+  base::Lock* lock(PpapiGlobals::Get()->GetProxyLock());
+  if (lock)
+    lock->Release();
 }
 
 }  // namespace ppapi