Record the time since Chromium is in background for background data use

Record the time since Chromium is in background for background data use

DataUse.BackgroundToDataRecievedPerByte.[User|System] histogram is
recorded for each background downstream byte.

DataUse.BackgroundToFirstDownstream.[User|System] histogram is
recorded for the first background downstream byte.

BUG=648808
Review-Url: https://chromiumcodereview.appspot.com/2417773005
Cr-Commit-Position: refs/heads/master@{#426386}
(cherry picked from commit 8766555a6c807796f6c177a3fe4ed81598620324)

Committed: https://chromium.googlesource.com/chromium/src/+/d0da84daf2f9b33da3849d2073875f989e183901

[Raj, 2016-10-31 01:55:41]

Description was changed from

==========
Record the time since Chromium is in background for background data use

DataUse.BackgroundToDataRecievedPerByte.[User|System] histogram is
recorded for each background downstream byte.

DataUse.BackgroundToFirstDownstream.[User|System] histogram is
recorded for the first background downstream byte.

BUG=648808

Review-Url: https://chromiumcodereview.appspot.com/2417773005
Cr-Commit-Position: refs/heads/master@{#426386}
(cherry picked from commit 8766555a6c807796f6c177a3fe4ed81598620324)
==========

to

==========
Record the time since Chromium is in background for background data use

DataUse.BackgroundToDataRecievedPerByte.[User|System] histogram is
recorded for each background downstream byte.

DataUse.BackgroundToFirstDownstream.[User|System] histogram is
recorded for the first background downstream byte.

BUG=648808

Review-Url: https://chromiumcodereview.appspot.com/2417773005
Cr-Commit-Position: refs/heads/master@{#426386}
(cherry picked from commit 8766555a6c807796f6c177a3fe4ed81598620324)

Committed:
https://chromium.googlesource.com/chromium/src/+/d0da84daf2f9b33da3849d207387...
==========

[Raj, 2016-10-31 01:55:42]

Committed patchset #1 (id:1) manually as
d0da84daf2f9b33da3849d2073875f989e183901.