Added early return in WebCore::TextResourceDecoder::checkForCSSCharset to fix buffer overflow

Added early return in WebCore::TextResourceDecoder::checkForCSSCharset to fix buffer overflow

Backported from Webkit: http://trac.webkit.org/changeset/169318 (patch by ddkilzer@apple.com) with a modified test to work for Blink.

BUG=376800
R=eseidel

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=174925

[eseidel, 2014-05-28 00:42:51]

lgtm

https://codereview.chromium.org/298023006/diff/40001/Source/core/html/parser/...
File Source/core/html/parser/TextResourceDecoder.cpp (right):

https://codereview.chromium.org/298023006/diff/40001/Source/core/html/parser/...
Source/core/html/parser/TextResourceDecoder.cpp:267: if (pos == dataEnd)
Seems like we should wrap this in a helper which returns pos != dataEnd, but OK.

[commit-bot: I haz the power, 2014-05-28 00:43:17]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/oysteine@chromium.org/298023006/40001

[commit-bot: I haz the power, 2014-05-28 02:11:05]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/9722)
  mac_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/9179)

[commit-bot: I haz the power, 2014-05-28 02:56:17]

Change committed as 174925