BitmapContentLayerUpdater shouldn't reallocate bitmap smaller.

BitmapContentLayerUpdater shouldn't reallocate bitmap smaller.

BitmapContentLayerUpdater was always allocating a new bitmap if the size of the region to be drawn changed, even if the new region was smaller. These unnecessary reallocations can be very expensive because they require page faults and for the operating system to clear out the memory.

BUG=296423
R=ben@chromium.org, enne@chromium.org, vangelis@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=225751

[enne (OOO), 2013-09-26 18:35:03]

lgtm

[Vangelis Kokkevis, 2013-09-26 18:49:49]

lgtm

[jbauman, 2013-09-27 00:42:15]

Also adding ben@ to review the layer_unittest.cc change.

[Ben Goodger (Google), 2013-09-27 04:47:19]

lgtm

[commit-bot: I haz the power, 2013-09-27 05:11:11]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jbauman@chromium.org/24486002/26001

[commit-bot: I haz the power, 2013-09-27 08:53:04]

Retried try job too often on linux_aura for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_aura...

[commit-bot: I haz the power, 2013-09-27 10:51:19]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jbauman@chromium.org/24486002/26001

[commit-bot: I haz the power, 2013-09-27 15:44:30]

Retried try job too often on linux_aura for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_aura...

[jbauman, 2013-09-27 19:13:14]

Committed patchset #4 manually as r225751 (presubmit successful).