Do PPB_FileIO Query and Read in the plugin process.

ppapi/shared_impl/tracked_callback.cc

Index: ppapi/shared_impl/tracked_callback.cc
diff --git a/ppapi/shared_impl/tracked_callback.cc b/ppapi/shared_impl/tracked_callback.cc
index 854e9dfb1509ebb843cdbc9633b1c6aca5371f5a..d98d56bf2138d9c5e6169c4a2577562acfbabfbf 100644
--- a/ppapi/shared_impl/tracked_callback.cc
+++ b/ppapi/shared_impl/tracked_callback.cc
@@ -128,11 +128,18 @@ void TrackedCallback::Run(int32_t result) {
       PostRun(result);
       return;
     }
-    // Copy |callback_| now, since |MarkAsCompleted()| may delete us.
+
+    // Copy callback fields now, since |MarkAsCompleted()| may delete us.
     PP_CompletionCallback callback = callback_;
+    CompletionTask completion_task = completion_task_;
+    completion_task_.Reset();
     // Do this before running the callback in case of reentrancy (which
     // shouldn't happen, but avoid strange failures).
     MarkAsCompleted();
+
+    if (!completion_task.is_null())
+      result = completion_task.Run(result);
+
     // TODO(dmichael): Associate a message loop with the callback; if it's not
     // the same as the current thread's loop, then post it to the right loop.
     CallWhileUnlocked(PP_RunCompletionCallback, &callback, result);
@@ -164,6 +171,12 @@ void TrackedCallback::PostRun(int32_t result) {
   is_scheduled_ = true;
 }
 
+void TrackedCallback::set_completion_task(
+    const CompletionTask& completion_task) {
+  DCHECK(completion_task_.is_null());
+  completion_task_ = completion_task;
+}
+
 // static
 bool TrackedCallback::IsPending(
     const scoped_refptr<TrackedCallback>& callback) {
@@ -195,7 +208,13 @@ int32_t TrackedCallback::BlockUntilComplete() {
 
   while (!completed())
     operation_completed_condvar_->Wait();
-  return result_for_blocked_callback_;
+
+  int32_t result = result_for_blocked_callback_;
+  if (!completion_task_.is_null()) {
+    result = completion_task_.Run(result);
+    completion_task_.Reset();
+  }
+  return result;
 }
 
 void TrackedCallback::MarkAsCompleted() {