Add UMA to study the effect of defaulting fullscreen video to landscape mode

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 8c420b2decee8dc16f7e733d5c01c7c725646ea1..67631c30ae236db6233557f01e11b6583b9e7ba2 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -10417,6 +10417,71 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="MobileFullscreenVideo.DurationAfterPotraitRotation"
+    units="milliseconds">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the duration that a fullscreen video is played after device
+    rotates from portrait to landscape mode for the first time, and before it
+    exits fullscreen. If there is no device rotation or if the video starts with
+    landscape mode, it is not recorded. If there are mutiple rotations between
+    portrait and landscape mode, only one record is emitted.

[Mark P, 2014/05/23 19:09:14]

Does this record the whole elapsed time the video is playing, or the time the
video is playing until exiting landscape mode?
i.e., does it behalf like the last sentence in the next histogram?

[qinmin, 2014/05/23 21:58:14]

This is equal to the time period from the first switch to the moment when video
exits fullscreen. Updated the comment.

On 2014/05/23 19:09:14, Mark P wrote:

+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.LandscapeDuration" units="milliseconds">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the duration that a fullscreen video is played in landscape
+    mode. If a video starts playing in landscape mode, and then it is switched
+    back and forth between landscape and portrait mode, only the time period
+    before the first switch is accounted.

[Mark P, 2014/05/23 19:09:14]

If a video starts playing in portrait mode, then the user switches to landscape
mode, do we also count those entries?

note to self: once we agree on a description, make PortraitDuration read the
same.

[qinmin, 2014/05/23 21:58:14]

no, it was not counted. Added the comment here.

On 2014/05/23 19:09:14, Mark P wrote:

+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.LandscapeRotation" enum="BooleanEnabled">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records whether a fullscreen video is switched from landscape to
+    portrait mode at any point during playback.
+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.OrientationPortrait"
+    enum="BooleanEnabled">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the device orientation when a video enters fullscreen. The
+    value is true if device orientation is portrait, or false otherwise. The
+    video doesn't necessarily needs to be in a playing state.
+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.PortraitDuration" units="milliseconds">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the duration that a fullscreen video is played in portrait
+    mode. If a video is switched from portrait to landscape mode during the
+    playback, only the time period before the switch is accounted.
+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.PortraitRotation" enum="BooleanEnabled">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records whether a fullscreen video is switched from portrait to
+    landscape mode at any point during playback.
+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.VideoPortrait" enum="BooleanEnabled">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records whether a video has a larger height than width when it
+    enters the fullscreen mode.
+  </summary>
+</histogram>
+
 <histogram name="MobileStartup.MobileMultiWindowInstances">
   <owner>dtrainor@chromium.org</owner>
   <summary>