Revert 187427 "PPAPI: Remove threading options; it's always on"

ppapi/proxy/plugin_globals.cc

Index: ppapi/proxy/plugin_globals.cc
===================================================================
--- ppapi/proxy/plugin_globals.cc	(revision 187715)
+++ ppapi/proxy/plugin_globals.cc	(working copy)
@@ -49,36 +49,40 @@
 PluginGlobals::PluginGlobals()
     : ppapi::PpapiGlobals(),
       plugin_proxy_delegate_(NULL),
-      callback_tracker_(new CallbackTracker) {
+      callback_tracker_(new CallbackTracker),
+      loop_for_main_thread_(
+          new MessageLoopResource(MessageLoopResource::ForMainThread())) {
+#if defined(ENABLE_PEPPER_THREADING)
+  enable_threading_ = true;
+#else
+  enable_threading_ = false;
+#endif
+
   DCHECK(!plugin_globals_);
   plugin_globals_ = this;
-
-  // ResourceTracker asserts that we have the lock when we add new resources,
-  // so we lock when creating the MessageLoopResource even though there is no
-  // chance of race conditions.
-  ProxyAutoLock lock;
-  loop_for_main_thread_ =
-      new MessageLoopResource(MessageLoopResource::ForMainThread());
 }
 
 PluginGlobals::PluginGlobals(PerThreadForTest per_thread_for_test)
     : ppapi::PpapiGlobals(per_thread_for_test),
       plugin_proxy_delegate_(NULL),
       callback_tracker_(new CallbackTracker) {
+#if defined(ENABLE_PEPPER_THREADING)
+  enable_threading_ = true;
+#else
+  enable_threading_ = false;
+#endif
   DCHECK(!plugin_globals_);
 }
 
 PluginGlobals::~PluginGlobals() {
   DCHECK(plugin_globals_ == this || !plugin_globals_);
-  {
-    ProxyAutoLock lock;
-    // Release the main-thread message loop. We should have the last reference
-    // count, so this will delete the MessageLoop resource. We do this before
-    // we clear plugin_globals_, because the Resource destructor tries to access
-    // this PluginGlobals.
-    DCHECK(!loop_for_main_thread_ || loop_for_main_thread_->HasOneRef());
-    loop_for_main_thread_ = NULL;
-  }
+  // Release the main-thread message loop. We should have the last reference
+  // count, so this will delete the MessageLoop resource. We do this before
+  // we clear plugin_globals_, because the Resource destructor tries to access
+  // this PluginGlobals.
+  DCHECK(!loop_for_main_thread_ || loop_for_main_thread_->HasOneRef());
+  loop_for_main_thread_ = NULL;
+
   plugin_globals_ = NULL;
 }
 
@@ -127,7 +131,9 @@
 }
 
 base::Lock* PluginGlobals::GetProxyLock() {
-  return &proxy_lock_;
+  if (enable_threading_)
+    return &proxy_lock_;
+  return NULL;
 }
 
 void PluginGlobals::LogWithSource(PP_Instance instance,