Augment message_loop with ability for custom UI message pumps (issue 576536)

base/message_loop/message_loop.h

 // Copyright 2013 The Chromium Authors. All rights reserved.

[Mark Mentovai, 2016/01/25 14:54:55]

Give this change an appropriate description. The description becomes the commit
message, and nobody knows or cares what bug 123456 is when they’re scanning
commit messages.

 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 
 #include <queue>
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 380 matching lines @@
   // tasks.
   debug::TaskAnnotator* task_annotator() { return &task_annotator_; }
 
   // Runs the specified PendingTask.
   void RunTask(const PendingTask& pending_task);
 
   //----------------------------------------------------------------------------
  protected:
   scoped_ptr<MessagePump> pump_;
 
+  using MessagePumpFactoryCallback = Callback<scoped_ptr<MessagePump>()>;
+
+  // Common protected constructor. Other constructors delegate the
+  // initialization to this constructor.
+  MessageLoop(Type type, MessagePumpFactoryCallback pump_factory);
+
+  // Configure various members and bind this message loop to the current thread.

[Mark Mentovai, 2016/01/25 14:54:54]

Since this is now protected, you should say when and how it’s expected to be
used, like how you adapted the constructor comment above.

+  void BindToCurrentThread();
+
  private:
   friend class RunLoop;
   friend class internal::IncomingTaskQueue;
   friend class ScheduleWorkTest;
   friend class Thread;
   FRIEND_TEST_ALL_PREFIXES(MessageLoopTest, DeleteUnboundLoop);
 
-  using MessagePumpFactoryCallback = Callback<scoped_ptr<MessagePump>()>;
-
   // Creates a MessageLoop without binding to a thread.
   // If |type| is TYPE_CUSTOM non-null |pump_factory| must be also given
   // to create a message pump for this message loop.  Otherwise a default
   // message pump for the |type| is created.
   //
   // It is valid to call this to create a new message loop on one thread,
   // and then pass it to the thread where the message loop actually runs.
   // The message loop's BindToCurrentThread() method must be called on the
   // thread the message loop runs on, before calling Run().
   // Before BindToCurrentThread() is called, only Post*Task() functions can
   // be called on the message loop.
   static scoped_ptr<MessageLoop> CreateUnbound(
       Type type,
       MessagePumpFactoryCallback pump_factory);
 
-  // Common private constructor. Other constructors delegate the initialization
-  // to this constructor.
-  MessageLoop(Type type, MessagePumpFactoryCallback pump_factory);
-
-  // Configure various members and bind this message loop to the current thread.
-  void BindToCurrentThread();
-
   // Sets the ThreadTaskRunnerHandle for the current thread to point to the
   // task runner for this message loop.
   void SetThreadTaskRunnerHandle();
 
   // Invokes the actual run loop using the message pump.
   void RunHandler();
 
   // Called to process any delayed non-nestable tasks.
   bool ProcessNextDelayedNonNestableTask();
 
@@ skipping 113 matching lines @@
 // MessageLoop instantiated with TYPE_UI.
 //
 // This class is typically used like so:
 //   MessageLoopForUI::current()->...call some method...
 //
 class BASE_EXPORT MessageLoopForUI : public MessageLoop {
  public:
   MessageLoopForUI() : MessageLoop(TYPE_UI) {
   }
 
+  explicit MessageLoopForUI(scoped_ptr<MessagePump> pump);
+
   // Returns the MessageLoopForUI of the current thread.
   static MessageLoopForUI* current() {
     MessageLoop* loop = MessageLoop::current();
     DCHECK(loop);
-    DCHECK_EQ(MessageLoop::TYPE_UI, loop->type());
+    DCHECK(loop->IsType(MessageLoop::TYPE_UI));
     return static_cast<MessageLoopForUI*>(loop);
   }
 
   static bool IsCurrent() {
     MessageLoop* loop = MessageLoop::current();
-    return loop && loop->type() == MessageLoop::TYPE_UI;
+    return loop && loop->IsType(MessageLoop::TYPE_UI);
   }
 
 #if defined(OS_IOS)
   // On iOS, the main message loop cannot be Run().  Instead call Attach(),
   // which connects this MessageLoop to the UI thread's CFRunLoop and allows
   // PostTask() to work.
   void Attach();
 #endif
 
 #if defined(OS_ANDROID)
@@ skipping 97 matching lines @@
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 static_assert(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
               "MessageLoopForIO should not have extra member variables");
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_