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 59fabd637c9b86147b3e5715b9fd6f2b9a5e5952..21e8cc1ff0e5bca9d0b37324092801c27539f427 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -10375,6 +10375,62 @@ 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. If there is no device rotation or

[Mark P, 2014/05/21 18:17:45]

I understand when the timer starts, but it's not clear when it ends.  If I
rotate the device from portrait to landscape mode, let the video play for a
while, then rotate it back and let it play more, what time gets recorded?  Does
the time stop when I rotate it back, or does it continue as long as the video is
playing?

Another case to consider: start video in portrait, rotate to landscape, rotate
to portrait, rotate to landscape.  Does the second rotate from portrait to
landscape cause a second emission to this histogram?

[qinmin, 2014/05/23 01:03:58]

Modified the comments a little bit. The recorded time period is the time after
the first portrait->landscape rotation happens and before video exits
fullscreen.
So 2nd rotate from portrait to landscape won't cause an emission.

On 2014/05/21 18:17:45, Mark P wrote:

+    if the video starts with landscape mode, it is not be recorded.
+  </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 is switched from landscape to portrait mode during the
+    playback, only the time period before the switch is accounted.

[Mark P, 2014/05/21 18:17:45]

Is this emitted when the rotation event happens or when the video stops playing?
i.e., suppose I play video for 5 seconds in landscape mode, then I switch to
portrait mode, play for 10 more seconds, and then switch to landscape mode again
and play for 20 more seconds.
What do you record:
* 5 seconds (and nothing else)
* 5 seconds and 20 seconds (two separate buckets)
* 25 seconds
?

Once we agree on a better description for this histogram, we should revise
PortraitDuration to be analogous.

[qinmin, 2014/05/23 01:03:58]

Only one record is emitted during one fullscreen playback. 
So if user plays video for 5 seconds in landscape mode for 5 seconds, and switch
back and force between landscape and portrait mode, only the first 5 seconds is
recorded.

On 2014/05/21 18:17:45, Mark P wrote:

+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.OrientationPortrait"
+    enum="BooleanEnabled">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the device orientation when video enters fullscreen. The

[Mark P, 2014/05/21 18:17:45]

Does it have to be playing at the time?  Can it, for instance, be paused?

[Mark P, 2014/05/21 18:17:45]

nit: when video -> when a video

[qinmin, 2014/05/23 01:03:58]

Done.

[qinmin, 2014/05/23 01:03:58]

No, video doesn't needs to be playing. Screenshot will be shown if video is
paused, so a user may switch between landscape and portrait mode once they saw
the screenshot.

On 2014/05/21 18:17:45, Mark P wrote:

+    value is true if device orientation is portrait, or false otherwise.
+  </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">

[Mark P, 2014/05/21 18:17:45]

You might want to have a LandscapeRotation for comparison purposes.

[qinmin, 2014/05/23 01:03:58]

Done.

+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the number of times that fullscreen video is switched from

[Mark P, 2014/05/21 18:17:45]

This histogram doesn't record a number as the description states.  It records a
boolean value.  Perhaps you want to replace your entire description with
something like:
Android: Records whether a fullscreen video is switched from portrait to
landscape mode at any point during playback.

(I think this covers everything that you tried to say in your original
description.)

[qinmin, 2014/05/23 01:03:58]

Done.

+    portrait mode to landscape mode. The value is true if a switch happens
+    during the playback, or false otherwise. If there are multiple switches
+    during the playback, only the first switch is recorded.
+  </summary>
+</histogram>
+
+<histogram name="MobileFullscreenVideo.VideoPortrait" enum="BooleanEnabled">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the number of fullscreen video that have a larger height

[Mark P, 2014/05/21 18:17:45]

nit: video -> videos

[qinmin, 2014/05/23 01:03:58]

changed to "a fullscreen video"

On 2014/05/21 18:17:45, Mark P wrote:

+    than width. The value is true if video height is larger than width, or false
+    otherwise.

[Mark P, 2014/05/21 18:17:45]

This histogram need to explicitly say when it is recorded.

[qinmin, 2014/05/23 01:03:58]

Done.

+  </summary>
+</histogram>
+
 <histogram name="MobileStartup.MobileMultiWindowInstances">
   <owner>dtrainor@chromium.org</owner>
   <summary>