Make a fairer combined message loop

base/message_loop/message_loop.cc

 // Copyright 2013 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 "base/message_loop/message_loop.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 606 matching lines @@
     // tasks (to faciliate FIFO sorting when two tasks have the same
     // delayed_run_time value) and for identifying the task in about:tracing.
     pending_task->sequence_num = next_sequence_num_++;
 
     TRACE_EVENT_FLOW_BEGIN0("task", "MessageLoop::PostTask",
         TRACE_ID_MANGLE(GetTaskTraceID(*pending_task, this)));
 
     bool was_empty = incoming_queue_.empty();
     incoming_queue_.push(*pending_task);
     pending_task->task.Reset();
-    if (!was_empty)
+    if (!was_empty && !IsType(TYPE_UI))

[klobag.chromium, 2013/06/28 20:57:13]

Do you need this to get ScheduleWork() called? Should it inside #if ANDROID?

[Kristian Monsen, 2013/06/28 21:04:41]

Yes, this is to avoid early out and always get ScheduleWork called on the UI
message loop on Android. If it has a performance impact on other platforms we
can add an #ifdef ANDROID, but want to avoid that if possible.

[joth, 2013/07/01 19:28:54]

Might be cleaner to delegate this to the pump:
if (!was_empty && !pump->NeedsScheduleWorkPerTask()) ...


also, It would be easy for someone to regress this and break android. Can we
think of anyway to add a test for this?

[Kristian Monsen, 2013/07/02 21:32:27]

Delegated to the pump.

       return true;  // Someone else should have started the sub-pump.
 
     pump = pump_;
   }
   // Since the incoming_queue_ may contain a task that destroys this message
   // loop, we cannot exit incoming_queue_lock_ until we are done with |this|.
   // We use a stack-based reference to the message pump so that we can call
   // ScheduleWork outside of incoming_queue_lock_.
 
   pump->ScheduleWork();
@@ skipping 187 matching lines @@
       fd,
       persistent,
       mode,
       controller,
       delegate);
 }
 
 #endif
 
 }  // namespace base