Mojo: Optimize VerifyUserPointer().

Mojo: Optimize VerifyUserPointer().

Gets rid of run-time division. In the new empty read test, goes from ~8.7
million iterations/second to ~9.7 million iterations/second (and in perf makes
VerifyUserPointer() go from ~10% to ~0.5%).

R=darin

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=226422

[darin (slow to review), 2013-09-30 21:09:55]

LGTM

[commit-bot: I haz the power, 2013-10-01 22:18:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/viettrungluu@chromium.org/25323003/1

[commit-bot: I haz the power, 2013-10-01 23:16:10]

Sorry for I got bad news for ya.
Compile failed with a clobber build on win_x64_rel.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_x64_re...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-10-01 23:17:55]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/viettrungluu@chromium.org/25323003/1

[commit-bot: I haz the power, 2013-10-01 23:49:42]

Sorry for I got bad news for ya.
Compile failed with a clobber build on win_x64_rel.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_x64_re...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-10-02 00:16:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/viettrungluu@chromium.org/25323003/1

[commit-bot: I haz the power, 2013-10-02 00:48:56]

Sorry for I got bad news for ya.
Compile failed with a clobber build on win_x64_rel.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_x64_re...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-10-02 04:30:23]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/viettrungluu@chromium.org/25323003/1

[commit-bot: I haz the power, 2013-10-02 07:42:25]

Change committed as 226422