Do PPB_FileIO Query and Read in the plugin process.

ppapi/shared_impl/tracked_callback.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_
 #define PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_
 
 #include <map>
 #include <set>
 
@@ skipping 94 matching lines @@
   // params and Run |callback|.
   // NOTE: an aborted callback has not necessarily completed, so a false result
   // doesn't imply that the callback has completed.
   // As a convenience, if |callback| is null, this returns false.
   static bool IsPending(const scoped_refptr<TrackedCallback>& callback);
 
   // Helper to determine if the given callback is scheduled to run on another
   // message loop.
   static bool IsScheduledToRun(const scoped_refptr<TrackedCallback>& callback);
 
- protected:
+  // Returns true if this is a blocking callback.
   bool is_blocking() {
     return !callback_.func;
   }
 
+ protected:
   bool is_required() {
     return (callback_.func &&
             !(callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL));
   }
   bool is_optional() {
     return (callback_.func &&
             (callback_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL));
   }
   bool has_null_target_loop() const { return target_loop_.get() == NULL; }
 
@@ skipping 35 matching lines @@
   // callback. Note that in-process, there is no lock, blocking callbacks are
   // not allowed, and therefore this pointer will be NULL.
   scoped_ptr<base::ConditionVariable> operation_completed_condvar_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(TrackedCallback);
 };
 
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_TRACKED_CALLBACK_H_