Remove CompressibleStringImpl::s_isPageBackground

Remove CompressibleStringImpl::s_isPageBackground

This CL removes a static variable s_isPageBackground which is used to
tell the current tab is in background or foreground. It is because it's
almost impossible to tell this.

For example,  one renderer process of a new tab page is used for
multiple tabs. Another example is that reloading a page will re-use the
process with a new Page object and updating a static variable along with
reloading will be complex.

After this CL, we won't be able to get the number of decompression only
in a background tab. With the new UMA, we can't give a go-sign for
CompressibleString but at least we can give a no-go-sign.

BUG=581266
TEST=n/a

Committed: https://crrev.com/01b6c4d4696d85645e0db3fc602b8da9203ce748
Cr-Commit-Position: refs/heads/master@{#372012}

[hajimehoshi, 2016-01-27 12:06:10]

hajimehoshi@chromium.org changed reviewers:
+ haraken@chromium.org, isherman@chromium.org

[hajimehoshi, 2016-01-27 12:06:11]

PTAL

isherman, I updated histgrams.xml the way in which it might break the backward
compatibility. I'm not sure this is OK.

[haraken, 2016-01-27 12:09:32]

WebKit change LGTM

[Ilya Sherman, 2016-01-28 02:08:03]

histograms.xml lgtm with a warning:

https://codereview.chromium.org/1646443002/diff/1/tools/metrics/histograms/hi...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/1646443002/diff/1/tools/metrics/histograms/hi...
tools/metrics/histograms/histograms.xml:59163: +  <int value="1"
label="Decompressed in a background or a foreground tab"/>
Generally speaking, we recommend only making backwards-compatible changes to
histograms.  However, for fairly new histograms, that don't yet have very much
data, it's ok to make a non-backwards-compatible change if you think there's not
enough data to potentially cause confusion.  (Keep in mind that old versions of
Chrome will always have users, so there will always be data trickling in from
users of any versions that shipped between when you first added this metric and
this current change to it.)

[hajimehoshi, 2016-01-28 02:38:08]

The CQ bit was checked by hajimehoshi@chromium.org

[commit-bot: I haz the power, 2016-01-28 02:41:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1646443002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1646443002/1

[commit-bot: I haz the power, 2016-01-28 04:04:32]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-01-28 04:04:32]

Exceeded global retry quota

[hajimehoshi, 2016-01-28 04:21:00]

The CQ bit was checked by hajimehoshi@chromium.org

[commit-bot: I haz the power, 2016-01-28 04:21:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1646443002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1646443002/1

[commit-bot: I haz the power, 2016-01-28 04:27:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-28 04:28:45]

Description was changed from

==========
Remove CompressibleStringImpl::s_isPageBackground

This CL removes a static variable s_isPageBackground which is used to
tell the current tab is in background or foreground. It is because it's
almost impossible to tell this.

For example,  one renderer process of a new tab page is used for
multiple tabs. Another example is that reloading a page will re-use the
process with a new Page object and updating a static variable along with
reloading will be complex.

After this CL, we won't be able to get the number of decompression only
in a background tab. With the new UMA, we can't give a go-sign for
CompressibleString but at least we can give a no-go-sign.

BUG=581266
TEST=n/a
==========

to

==========
Remove CompressibleStringImpl::s_isPageBackground

This CL removes a static variable s_isPageBackground which is used to
tell the current tab is in background or foreground. It is because it's
almost impossible to tell this.

For example,  one renderer process of a new tab page is used for
multiple tabs. Another example is that reloading a page will re-use the
process with a new Page object and updating a static variable along with
reloading will be complex.

After this CL, we won't be able to get the number of decompression only
in a background tab. With the new UMA, we can't give a go-sign for
CompressibleString but at least we can give a no-go-sign.

BUG=581266
TEST=n/a

Committed: https://crrev.com/01b6c4d4696d85645e0db3fc602b8da9203ce748
Cr-Commit-Position: refs/heads/master@{#372012}
==========

[commit-bot: I haz the power, 2016-01-28 04:28:46]

Patchset 1 (id:??) landed as
https://crrev.com/01b6c4d4696d85645e0db3fc602b8da9203ce748
Cr-Commit-Position: refs/heads/master@{#372012}