PPAPI: Add unlocking for PPP calls and callbacks. Add more locking.

ppapi/proxy/ppp_instance_private_proxy.cc

Index: ppapi/proxy/ppp_instance_private_proxy.cc
diff --git a/ppapi/proxy/ppp_instance_private_proxy.cc b/ppapi/proxy/ppp_instance_private_proxy.cc
index 75e9d60e131e85bbd2d3b485ea53c0218b9d5df1..33f5ea4f4702e6607b3badf0dc815b7108502863 100644
--- a/ppapi/proxy/ppp_instance_private_proxy.cc
+++ b/ppapi/proxy/ppp_instance_private_proxy.cc
@@ -12,6 +12,7 @@
 #include "ppapi/proxy/plugin_dispatcher.h"
 #include "ppapi/proxy/plugin_resource_tracker.h"
 #include "ppapi/proxy/ppapi_messages.h"
+#include "ppapi/shared_impl/proxy_lock.h"
 
 namespace ppapi {
 namespace proxy {
@@ -74,7 +75,8 @@ void PPP_Instance_Private_Proxy::OnMsgGetInstanceObject(
     PP_Instance instance,
     SerializedVarReturnValue result) {
   result.Return(dispatcher(),
-                ppp_instance_private_impl_->GetInstanceObject(instance));
+                CallWhileUnlocked(ppp_instance_private_impl_->GetInstanceObject,
+                                  instance));
 }
 
 }  // namespace proxy