Adds the UserInputMonitor implementation for Windows.

media/media.gyp

Index: media/media.gyp
diff --git a/media/media.gyp b/media/media.gyp
index 1bdcbcacde0d8464abe592783978b6bdc7a22c9b..ba7df679bfbf4f64be8cabcbc4096f31135be1f1 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -635,8 +635,6 @@
             'audio/cras/cras_input.h',
             'audio/cras/cras_unified.cc',
             'audio/cras/cras_unified.h',
-            'base/keyboard_event_counter.cc',
-            'base/keyboard_event_counter.h',
           ],
         }],
         ['use_pulseaudio==1', {
@@ -830,6 +828,12 @@
             'ENABLE_EAC3_PLAYBACK',
           ],
         }],
+        ['OS!="linux" and OS!="win"', {
+          'sources!': [
+            'base/keyboard_event_counter.cc',
+            'base/keyboard_event_counter.h',
+          ],
+        }],
       ],
     },
     {
@@ -912,6 +916,7 @@
         'base/sinc_resampler_unittest.cc',
         'base/test_data_util.cc',
         'base/test_data_util.h',
+        'base/user_input_monitor_unittest.cc',
         'base/vector_math_testing.h',
         'base/vector_math_unittest.cc',
         'base/video_frame_unittest.cc',