PPAPI: Blocking callbacks shouldn't need a target_loop_

ppapi/shared_impl/tracked_callback.cc

 // 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.
 
 #include "ppapi/shared_impl/tracked_callback.h"
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 149 matching lines @@
     return;
   }
   if (result == PP_ERROR_ABORTED)
     aborted_ = true;
   // We might abort when there's already a scheduled callback, but callers
   // should never try to PostRun more than once otherwise.
   DCHECK(result == PP_ERROR_ABORTED || !is_scheduled_);
 
   base::Closure callback_closure(
       RunWhileLocked(base::Bind(&TrackedCallback::Run, this, result)));
-  if (!target_loop_.get()) {
+  if (is_blocking()) {
+    // We might not have a MessageLoop to post to, so we must call Run()
+    // directly.
+    callback_closure.Run();
+  } else if (!target_loop_.get()) {

[bbudge, 2013/09/04 22:29:19]

It seems like the most common case is last. Do you have a feel for the
likelihood of the different cases? Did you consider switching the ifs? In other
words,

if (target_loop_.get()) {
....post task to target_loop_
} else {
  if (is_blocking()) {
.....blocking code
  } else {
.....in-process code
  }
}

     // We must be running in-process and on the main thread (the Enter
     // classes protect against having a null target_loop_ otherwise).
     DCHECK(IsMainThread());
     DCHECK(PpapiGlobals::Get()->IsHostGlobals());
     base::MessageLoop::current()->PostTask(FROM_HERE, callback_closure);
   } else {
     target_loop_->PostClosure(FROM_HERE, callback_closure, 0);
   }
   is_scheduled_ = true;
 }
@@ skipping 51 matching lines @@
   // until we're done.
   scoped_refptr<TrackedCallback> thiz = this;
   completed_ = true;
   // We may not have a valid resource, in which case we're not in the tracker.
   if (resource_id_)
     tracker_->Remove(thiz);
   tracker_ = NULL;
 }
 
 }  // namespace ppapi