Do PPB_FileIO Query and Read in the plugin process.

ppapi/shared_impl/tracked_callback.h

Index: ppapi/shared_impl/tracked_callback.h
diff --git a/ppapi/shared_impl/tracked_callback.h b/ppapi/shared_impl/tracked_callback.h
index 4917990e3cfeafa31ebb70623bc4538c1685b3a9..c4bf5cfd279d3c23fe134835301c94a5001584a3 100644
--- a/ppapi/shared_impl/tracked_callback.h
+++ b/ppapi/shared_impl/tracked_callback.h
@@ -98,6 +98,11 @@ class PPAPI_SHARED_EXPORT TrackedCallback
   // completion.
   bool aborted() const { return aborted_; }
 
+  // Returns true if this is a blocking callback.
+  bool is_blocking() {
+    return !callback_.func;
+  }
+
   // Determines if the given callback is pending. A callback is pending if it
   // has not completed and has not been aborted. When receiving a plugin call,
   // use this to detect if |callback| represents an operation in progress. When
@@ -113,10 +118,6 @@ class PPAPI_SHARED_EXPORT TrackedCallback
   static bool IsScheduledToRun(const scoped_refptr<TrackedCallback>& callback);
 
  protected:
-  bool is_blocking() {
-    return !callback_.func;
-  }
-
   bool is_required() {
     return (callback_.func &&
             !(callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL));