Add UMA to study the video types for mobile

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 8321fe938ca8b6b30f954385cee757219bb4be5c..7cd96ee4f2e7e5a24baba91f5e66b347ed1cfafe 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -12249,6 +12249,21 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="MobileVideo.IsRegularVideoUrl" enum="BooleanEnabled">

[Ilya Sherman, 2014/08/26 19:54:29]

Please use a custom enum, rather than "BooleanEnabled".

[Ilya Sherman, 2014/08/26 19:54:29]

What do you think of naming this histogram something more like
"Media.Video.Mobile.IsRegularVideoUrl"?  The UMA dashboard is a little easier to
use when there aren't a bunch of tiny groups, but rather a smaller number of
bigger top-level groups.

[qinmin, 2014/08/27 00:10:00]

Done. added MediaType Enum

[qinmin, 2014/08/27 00:10:00]

Changed this to Media.Mobile.MediaType and updated the description

On 2014/08/26 19:54:29, Ilya Sherman wrote:

+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records whether a video is a regular video url rather than is

[Ilya Sherman, 2014/08/26 19:54:29]

nit: "rather than is" -> "rather than one that is"

[qinmin, 2014/08/27 00:10:00]

Done.

+    created through MediaSource.
+  </summary>
+</histogram>
+
+<histogram name="MobileVideo.IsVideoUrlHLSVideo" enum="BooleanEnabled">

[Ilya Sherman, 2014/08/26 19:54:29]

nit: I'd prefer that you spell out the acronym in the name.  How about
"IsHttpLiveStreamingVideo", or something like that?

[qinmin, 2014/08/27 00:10:00]

Done.

+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Whether a regular video url is an HLS(Http live streaming) video.

[Ilya Sherman, 2014/08/26 19:54:29]

nit: "HLS(Http live streaming)" -> "HLS (http live streaming)"

[qinmin, 2014/08/27 00:10:00]

Done.

+  </summary>
+</histogram>
+
 <histogram name="Mouse.PointerSensitivity.Changed" enum="PointerSensitivity">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>