Add a unified resource tracker shared between the proxy and the impl.

ppapi/proxy/plugin_dispatcher.cc

Index: ppapi/proxy/plugin_dispatcher.cc
diff --git a/ppapi/proxy/plugin_dispatcher.cc b/ppapi/proxy/plugin_dispatcher.cc
index 53dab265f5b6750f38eb402c4979be112cb64c95..fea4de6fcb93c9226e7dc62b913755e4d5985b1e 100644
--- a/ppapi/proxy/plugin_dispatcher.cc
+++ b/ppapi/proxy/plugin_dispatcher.cc
@@ -24,6 +24,7 @@
 #include "ppapi/proxy/ppb_instance_proxy.h"
 #include "ppapi/proxy/ppp_class_proxy.h"
 #include "ppapi/proxy/resource_creation_proxy.h"
+#include "ppapi/shared_impl/resource.h"
 #include "ppapi/shared_impl/tracker_base.h"
 
 #if defined(OS_POSIX)
@@ -31,6 +32,8 @@
 #include "ipc/ipc_channel_posix.h"
 #endif
 
+using ppapi::Resource;
+
 namespace pp {
 namespace proxy {
 
@@ -74,6 +77,11 @@ PluginDispatcher* PluginDispatcher::GetForInstance(PP_Instance instance) {
 }
 
 // static
+PluginDispatcher* PluginDispatcher::GetForResource(const Resource* resource) {
+  return GetForInstance(resource->pp_instance());
+}
+
+// static
 const void* PluginDispatcher::GetInterfaceFromDispatcher(
     const char* interface) {
   // All interfaces the plugin requests of the browser are "PPB".