WTF::notFound looks too much like a local variable.

WTF::notFound looks too much like a local variable.

I discovered this as part of attempting to deploy -Wshadow.
There was one place (HashMap.h) where we had a notFound local.

Changing notFound to kNotFound also made it look pretty in my editor.

This sorta seems like a silly change, but I do believe it will help
code readability.  I think it was a mistake to have a global constant
beginging with a lowercase letter in the first place.

BUG=294205
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=158058

[abarth-chromium, 2013-09-19 18:35:44]

LGTM

[commit-bot: I haz the power, 2013-09-19 19:39:58]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/eseidel@chromium.org/23464095/1

[commit-bot: I haz the power, 2013-09-19 22:04:59]

Change committed as 158058