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.cc b/base/message_loop/message_loop.cc
index cf0b31c..cdd8721 100644
--- a/base/message_loop/message_loop.cc
+++ b/base/message_loop/message_loop.cc
@@ -425,7 +425,8 @@
 
   StartHistogrammer();
 
-#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID) && \
+    !defined(USE_GTK_MESSAGE_PUMP)
   if (run_loop_->dispatcher_ && type() == TYPE_UI) {
     static_cast<MessagePumpForUI*>(pump_.get())->
         RunWithDispatcher(this, run_loop_->dispatcher_);