Fix Telemetry to calculate bounding visible rect correctly.

Fix Telemetry to calculate bounding visible rect correctly.

Fixes the parts of bounding client rects which are to the left or to the
top of the visible area not to visible (in addition to the parts which
are to the right or to the bottom of the visible area).

Enhances the corresponding unittest to test these cases, too.

BUG=369479
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269116

[e.hakkinen, 2014-05-07 08:54:32]

Without this patch pincing, scrolling, swiping and tapping synthesized by
Telemetry on a scrolled page (i.e. when the top left corner of the visible area
is not the top left corner of the page) happen most often outside the visible
area. That is very artificial as a real user cannot do that.

[Dominik Grewe, 2014-05-07 09:20:49]

Sorry for the delay. LGTM but you still need owner's approval.

[bulach, 2014-05-07 09:22:41]

lgtm, thanks!

[e.hakkinen, 2014-05-07 10:02:50]

The CQ bit was checked by e.hakkinen@partner.samsung.com

[commit-bot: I haz the power, 2014-05-07 10:06:42]

CQ is trying da patch. Follow status at

https://chromium-status.appspot.com/cq/e.hakkinen@partner.samsung.com/2659330...

[commit-bot: I haz the power, 2014-05-07 16:11:27]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  android_dbg_triggered_tests on tryserver.chromium
  win_chromium_rel on tryserver.chromium

[commit-bot: I haz the power, 2014-05-07 18:24:35]

FYI, CQ is re-trying this CL (attempt #2).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  android_dbg_triggered_tests on tryserver.chromium
  win_chromium_rel on tryserver.chromium

[commit-bot: I haz the power, 2014-05-07 19:55:52]

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

[commit-bot: I haz the power, 2014-05-07 19:55:53]

Try jobs failed on following builders:
  android_dbg_triggered_tests on tryserver.chromium

[e.hakkinen, 2014-05-08 08:47:24]

The CQ bit was checked by e.hakkinen@partner.samsung.com

[commit-bot: I haz the power, 2014-05-08 08:47:53]

CQ is trying da patch. Follow status at

https://chromium-status.appspot.com/cq/e.hakkinen@partner.samsung.com/2659330...

[commit-bot: I haz the power, 2014-05-09 00:06:30]

Change committed as 269116