[message_loop] Remove message_loop_forward.h

As a final step, replace all includes back:
- mv message_loop_current.h message_loop.h
- s/message_loop_forward.h/message_loop.h/ in all includes.
- s/message_loop_forward.h/message_loop.h/ in base/BUILD.gn
- Remove message_loop_forward.h from third_party/DEPS.

[email protected]
[email protected]
BUG=891670

Change-Id: I623077025701459ddb7045cbcfdad138aa90a9e4
Reviewed-on: https://chromium-review.googlesource.com/c/1313110
Reviewed-by: Alexander Timin <[email protected]>
Reviewed-by: Gabriel Charette <[email protected]>
Cr-Commit-Position: refs/heads/master@{#604690}
diff --git a/remoting/base/auto_thread_unittest.cc b/remoting/base/auto_thread_unittest.cc
index 566598a8..595772e 100644
--- a/remoting/base/auto_thread_unittest.cc
+++ b/remoting/base/auto_thread_unittest.cc
@@ -6,7 +6,7 @@
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
-#include "base/message_loop/message_loop_forward.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/scoped_native_library.h"
 #include "base/single_thread_task_runner.h"