Remove mutation foot-gun from CSSPrimitiveValue

Remove mutation foot-gun from CSSPrimitiveValue

Misuse of this method could easily cause
memory leaks and UAFs. It wasn't actually doing anything
in the one place it was called, so I removed it.

I also fixed another FIXME about how unsigned/signed
constructors are confusing.  At least now we'll ASSERT
if you got the wrong one.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170029

[esprehn, 2014-03-23 06:14:49]

lgtm

https://codereview.chromium.org/209353004/diff/1/Source/core/css/CSSParserVal...
File Source/core/css/CSSParserValues.cpp (right):

https://codereview.chromium.org/209353004/diff/1/Source/core/css/CSSParserVal...
Source/core/css/CSSParserValues.cpp:91: // FIXME: Why do we have these
special-case ifs outside of the switch?
The switch is over CSSPrimitiveValue PrimitiveUnit values, but these are
CSSParserValues. This FIXME doesn't make sense.

[eseidel, 2014-03-26 05:01:10]

The CQ bit was checked by eseidel@chromium.org

[commit-bot: I haz the power, 2014-03-26 05:01:13]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/eseidel@chromium.org/209353004/20001

[commit-bot: I haz the power, 2014-03-26 05:30:44]

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

[commit-bot: I haz the power, 2014-03-26 05:30:44]

Try jobs failed on following builders:
  tryserver.blink on linux_blink_rel

[eseidel, 2014-03-26 06:30:32]

The CQ bit was checked by eseidel@chromium.org

[commit-bot: I haz the power, 2014-03-26 06:30:37]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/eseidel@chromium.org/209353004/20001

[commit-bot: I haz the power, 2014-03-26 07:05:58]

Change committed as 170029