Report WMPI components memory usage to UMA

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index b46177b82bebf5ec61d688bde1cee5c63b8989f4..4404a71d2c294cfa1fbdcf969dfb7c8e98079355 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -25741,6 +25741,38 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.WebMediaPlayerImpl.Memory.AudioKb" units="KB">

[watk, 2016/12/13 23:34:31]

I don't think putting Kb in the name is conventional because you have the units
as well.

[servolk, 2016/12/14 00:07:23]

I've noticed that some metrics in this file use Kb suffix even despite having
units=KB, e.g. Compositing.Renderer.PictureMemoryUsageKb or
PurgeAndSuspend.Memory.PartitionAllocKB or Sqlite.SizeKB, but you are right,
most of them don't use the Kb suffix, so dropped it.

+  <owner>servolk@chromium.org</owner>
+  <summary>
+    Amound of memory used by WebMediaPlayerImpl audio renderer when memory

[watk, 2016/12/13 23:34:31]

Amount.

"used by the"

[servolk, 2016/12/14 00:07:23]

Done.

+    pressure was reported.
+  </summary>
+</histogram>
+
+<histogram name="Media.WebMediaPlayerImpl.Memory.DataSourceKb" units="KB">
+  <owner>servolk@chromium.org</owner>
+  <summary>
+    Amound of memory used by WebMediaPlayerImpl data source when memory pressure
+    was reported.
+  </summary>
+</histogram>
+
+<histogram name="Media.WebMediaPlayerImpl.Memory.DemuxerKb" units="KB">
+  <owner>servolk@chromium.org</owner>
+  <summary>
+    Amound of memory used by WebMediaPlayerImpl demuxer when memory pressure was
+    reported.
+  </summary>
+</histogram>
+
+<histogram name="Media.WebMediaPlayerImpl.Memory.VideoKb" units="KB">
+  <owner>servolk@chromium.org</owner>
+  <summary>
+    Amound of memory used by WebMediaPlayerImpl video renderer when memory
+    pressure was reported.
+  </summary>
+</histogram>
+
 <histogram name="Media.WindowsCoreAudioInput" enum="BooleanSuccess">
   <owner>henrika@chromium.org</owner>
   <summary>