Web Inspector: Whitelist safe styles for 'console.log('%c...', ...)'.

https://bugs.webkit.org/show_bug.cgi?id=98945

Reviewed by Pavel Feldman.

Source/WebCore:

Support for styling console messages via '%c' landed without any
parsing of the style information provided. This means that it's fairly
simple to accidentally or maliciously break the console with cleverly
styled messages. To mitigate this risk, whitelisting a safe subset of
CSS seems appropriate.

As a first pass at a reasonable whitelist, this patch allows
'background[-*]', 'border[-*]', 'color[-*]', 'font[-*]',
'margin[-*]', 'padding[-*]', 'text[-*]', '-webkit-background[-*]',
'-webkit-border[-*]', '-webkit-font[-*]', '-webkit-margin[-*]',
'-webkit-padding[-*]', and '-webkit-text[-*]'.

Test: inspector/console/console-format-style-whitelist.html

* inspector/front-end/ConsoleMessage.js:
(WebInspector.ConsoleMessageImpl.prototype._formatWithSubstitutionString.styleFormatter):
    Create a buffer element onto which the user-provided styles are
    applied. Whitelisted styles are transfered from the buffer onto
    the actual console message.
(WebInspector.ConsoleMessageImpl.prototype._formatWithSubstitutionString.isWhitelistedProperty):
     Returns true if the specific style is whitelisted. Expects styles
     in the hyphenated form (that is, '-webkit-padding-start' rather than
     CSSOM's 'webkitPaddingStart').

LayoutTests:

* http/tests/inspector/console-test.js:
(initialize_ConsoleTest.InspectorTest.dumpConsoleMessagesWithStyles):
    Use the 'cssText' property of an element, rather than reading from
    its 'style' attribute. Also, gracefully handle unstyled elements
    by explicitly noting their emptyness.
* inspector/console/console-format-style-whitelist-expected.txt: Added.
* inspector/console/console-format-style-whitelist.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@131448 268f45cc-cd09-0410-ab3c-d52691b4dbfc