Fix regression caused by 11968032 in upgrading themes

BUG=177630
Test=Manual
1) Install a theme
2) Close Chrome
3) Change the value of kThemePackVersion to a different number in browser_theme_pack.cc
4) Compile Chrome
5) Reopen Chrome. Ensure that the theme is still present 

R=mpcomplete, erg
TBR=sky (For new includes in chrome_browser_extensions.gypi)

Review URL: https://chromiumcodereview.appspot.com/12326089

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@184340 0039d316-1c4b-4281-b951-d872f2087c98
7 files changed