Crash fix for desktop capture size calculations, and some minor things.

Crash fix for desktop capture size calculations, and some minor things.

When stress-testing desktop resize (by running a CrOS Ash desktop in a
window), a problem with the capture frame size calculations was
revealed: The max frame size was being updated for each change in
desktop size.  This meant that once width or height were reduced, they
could never be increased again.  When the width or height were reduced
to zero, Chrome would crash.

This change fixes the size calculation (the max size is made constant
from construction), adds a few extra sanity-checks to prevent crashes on
OOM or zero frame sizes, and also adds re-scaling of the rendered mouse
cursor bitmap whenever the desktop size has changed.

BUG=462799
TEST=Resized CrOS Ash-desktop-in-a-window on my local dev workstation to confirm crash is resolved.

Committed: https://crrev.com/db73faeca6f1a3a6cb2923afc2e0bc3ea995aee7
Cr-Commit-Position: refs/heads/master@{#318958}

[miu, 2015-02-28 03:03:16]

miu@chromium.org changed reviewers:
+ hshi@chromium.org

[miu, 2015-02-28 03:03:17]

hshi: Could you PTAL?

[hshi1, 2015-03-03 20:03:41]

lgtm

[miu, 2015-03-03 21:04:20]

The CQ bit was checked by miu@chromium.org

[commit-bot: I haz the power, 2015-03-03 21:05:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/965123002/1

[commit-bot: I haz the power, 2015-03-03 21:10:44]

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

[commit-bot: I haz the power, 2015-03-03 21:10:45]

Try jobs failed on following builders:
  android_aosp on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/android_aosp/bu...)
  ios_dbg_simulator_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...)
  ios_rel_device_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)

[miu, 2015-03-03 21:25:15]

The CQ bit was checked by miu@chromium.org

[miu, 2015-03-03 21:25:16]

The patchset sent to the CQ was uploaded after l-g-t-m from hshi@chromium.org
Link to the patchset: https://codereview.chromium.org/965123002/#ps20001 (title:
"rebase")

[commit-bot: I haz the power, 2015-03-03 21:26:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/965123002/20001

[commit-bot: I haz the power, 2015-03-03 23:12:04]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-03 23:12:51]

Patchset 2 (id:??) landed as
https://crrev.com/db73faeca6f1a3a6cb2923afc2e0bc3ea995aee7
Cr-Commit-Position: refs/heads/master@{#318958}