Update ppapi/ to use scoped_refptr<T>::get() rather than implicit "operator T*"

ppapi/shared_impl/var_tracker.cc

Index: ppapi/shared_impl/var_tracker.cc
diff --git a/ppapi/shared_impl/var_tracker.cc b/ppapi/shared_impl/var_tracker.cc
index 7ff7462e3e0542b5787c76faea78775fb5e64b01..771cde403f78032c25df9d6d50b314d1fbfb5ed9 100644
--- a/ppapi/shared_impl/var_tracker.cc
+++ b/ppapi/shared_impl/var_tracker.cc
@@ -199,7 +199,7 @@ PP_Var VarTracker::MakeArrayBufferPPVar(uint32 size_in_bytes) {
   CheckThreadingPreconditions();
 
   scoped_refptr<ArrayBufferVar> array_buffer(CreateArrayBuffer(size_in_bytes));
-  if (!array_buffer)
+  if (!array_buffer.get())
     return PP_MakeNull();
   return array_buffer->GetPPVar();
 }
@@ -229,7 +229,7 @@ PP_Var VarTracker::MakeArrayBufferPPVar(uint32 size_in_bytes,
 
   scoped_refptr<ArrayBufferVar> array_buffer(
       CreateShmArrayBuffer(size_in_bytes, handle));
-  if (!array_buffer)
+  if (!array_buffer.get())
     return PP_MakeNull();
   return array_buffer->GetPPVar();
 }