High DPI support for Themes

Modified processing of Theme URLs. We will now insert the scale factor text
before the first ? instead of just appending it. This is necessary for parsing
to work properly (see ParsePathAndScale in src/ui/webui/web_ui_util.cc).
See also recent CL which modified related *.css and *.js files:
https://codereview.chromium.org/16610002/

Example:
Old: url(chrome://theme/IDR_THEME_NTP_ATTRIBUTION?$1@2x)
New: url(chrome://theme/IDR_THEME_NTP_ATTRIBUTION?@2x$1)

BUG=chromium:248189,chromium:133934
TEST=ChromeHtmlUnittest.testThemeResources

Landing for sschmitz@chromium.org

Review URL: https://codereview.chromium.org/15713020/


git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@127 7262f16d-afe8-6277-6482-052fa10e57b1