Build Android's MessagePumpForUI by upstreaming SystemMessageHandler

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index f5bf4a9dddc62f1dd6a7861cf38a8dcec2724ba8..6b370754914f13f74154348626a60aba476a091d 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -485,9 +485,6 @@
               ['include', '^sys_info_linux\\.cc$'],
               ['include', '^sys_string_conversions_posix\\.cc$'],
               ['include', '^worker_pool_linux\\.cc$'],
-              # TODO(michaelbai): The below files are excluded because of the
-              # missing JNI, add them back when JNI is ready.
-              ['exclude', '^message_pump_android\\.cc$'],
             ],
           }],
           [ 'OS != "mac"', {