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

ppapi/proxy/plugin_globals.cc

Index: ppapi/proxy/plugin_globals.cc
diff --git a/ppapi/proxy/plugin_globals.cc b/ppapi/proxy/plugin_globals.cc
index 664fbebf22a93dccbea94d839dd98bdfaf6aa1c6..6d23ff8f97f46f2e5328359e0c430508346a24eb 100644
--- a/ppapi/proxy/plugin_globals.cc
+++ b/ppapi/proxy/plugin_globals.cc
@@ -19,8 +19,15 @@ PluginGlobals::PluginGlobals()
   plugin_globals_ = this;
 }
 
+PluginGlobals::PluginGlobals(ForTest for_test)
+    : ppapi::PpapiGlobals(for_test),
+      plugin_proxy_delegate_(NULL),
+      callback_tracker_(new CallbackTracker) {
+  DCHECK(!plugin_globals_);
+}
+
 PluginGlobals::~PluginGlobals() {
-  DCHECK(plugin_globals_ == this);
+  DCHECK(plugin_globals_ == this || !plugin_globals_);
   plugin_globals_ = NULL;
 }
 
@@ -51,5 +58,13 @@ PP_Module PluginGlobals::GetModuleForInstance(PP_Instance instance) {
   return 0;
 }
 
+base::Lock* PluginGlobals::GetProxyLock() {
+#ifdef ENABLE_PEPPER_THREADING
+  return &proxy_lock_;
+#else
+  return NULL;
+#endif
+}
+
 }  // namespace proxy
 }  // namespace ppapi