gtk: Some code cleanup for the message-pump.

GTK message-pump defines its own observer, but it has the same name as the
message-pump observers used in other platforms. So rename the GTK version
to MessagePumpGdkObserver.

Also, GTK version of message-pump dispatcher is never used, so get rid of
that.

BUG=145600
R=piman@chromium.org, thakis@chromium.org

Review URL: https://codereview.chromium.org/23537016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221846 0039d316-1c4b-4281-b951-d872f2087c98


CrOS-Libchrome-Original-Commit: 827d38ae4b2bbd630b8950edbb52a83c5329593f
diff --git a/base/message_loop/message_loop.h b/base/message_loop/message_loop.h
index db6aa9b..de602af 100644
--- a/base/message_loop/message_loop.h
+++ b/base/message_loop/message_loop.h
@@ -40,6 +40,7 @@
 #elif defined(USE_OZONE) && !defined(OS_NACL)
 #include "base/message_loop/message_pump_ozone.h"
 #else
+#define USE_GTK_MESSAGE_PUMP
 #include "base/message_loop/message_pump_gtk.h"
 #endif
 
@@ -49,6 +50,8 @@
 namespace base {
 
 class HistogramBase;
+class MessagePumpDispatcher;
+class MessagePumpObserver;
 class RunLoop;
 class ThreadTaskRunnerHandle;
 #if defined(OS_ANDROID)
@@ -90,7 +93,9 @@
 class BASE_EXPORT MessageLoop : public MessagePump::Delegate {
  public:
 
-#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
+#if defined(USE_GTK_MESSAGE_PUMP)
+  typedef MessagePumpGdkObserver Observer;
+#elif !defined(OS_MACOSX) && !defined(OS_ANDROID)
   typedef MessagePumpDispatcher Dispatcher;
   typedef MessagePumpObserver Observer;
 #endif