Fix self-assignment in pp::Resource

ppapi/cpp/resource.cc

Index: ppapi/cpp/resource.cc
diff --git a/ppapi/cpp/resource.cc b/ppapi/cpp/resource.cc
index 7daab4a4a52e60e42e4af849af84ea33b22c1fff..5a327d635937daabb1c46d90a5108bdc2f37df04 100644
--- a/ppapi/cpp/resource.cc
+++ b/ppapi/cpp/resource.cc
@@ -25,11 +25,11 @@ Resource::~Resource() {
 }
 
 Resource& Resource::operator=(const Resource& other) {
+  if (!other.is_null())
+    Module::Get()->core()->AddRefResource(other.pp_resource_);
   if (!is_null())
     Module::Get()->core()->ReleaseResource(pp_resource_);
   pp_resource_ = other.pp_resource_;
-  if (!is_null())
-    Module::Get()->core()->AddRefResource(pp_resource_);
   return *this;
 }