Implement MessagePumpMojo using WaitSet.

mojo/message_pump/message_pump_mojo.h

Index: mojo/message_pump/message_pump_mojo.h
diff --git a/mojo/message_pump/message_pump_mojo.h b/mojo/message_pump/message_pump_mojo.h
index 4dc0c2238f6e1d0f195f52f79f3210f05ea5447f..4bc07072408d626cebadc1c046675d2d80f0dfbb 100644
--- a/mojo/message_pump/message_pump_mojo.h
+++ b/mojo/message_pump/message_pump_mojo.h
@@ -69,7 +69,6 @@ class MOJO_MESSAGE_PUMP_EXPORT MessagePumpMojo : public base::MessagePump {
 
  private:
   struct RunState;
-  struct WaitState;
 
   // Contains the data needed to track a request to AddHandler().
   struct Handler {
@@ -94,17 +93,15 @@ class MOJO_MESSAGE_PUMP_EXPORT MessagePumpMojo : public base::MessagePump {
 
   // Removes the given invalid handle. This is called if MojoWaitMany finds an
   // invalid handle.
-  void RemoveInvalidHandle(const WaitState& wait_state,
-                           MojoResult result,
-                           uint32_t result_index);
+  void RemoveInvalidHandle(MojoResult result, Handle handle);
 
   void SignalControlPipe();
 
-  WaitState GetWaitState() const;
-
   // Returns the deadline for the call to MojoWaitMany().
   MojoDeadline GetDeadlineForWait(const RunState& run_state) const;
 
+  void SignalHandleReady(Handle handle);
+
   void WillSignalHandler();
   void DidSignalHandler();
 
@@ -132,6 +129,8 @@ class MOJO_MESSAGE_PUMP_EXPORT MessagePumpMojo : public base::MessagePump {
 
   base::ObserverList<Observer> observers_;
 
+  // Mojo handle for the wait set.
+  ScopedHandle wait_set_handle_;
   // Used to wake up run loop from |SignalControlPipe()|.
   ScopedMessagePipeHandle read_handle_;
   ScopedMessagePipeHandle write_handle_;