wstring: Remove the ability to put wstrings in hash_map<>s.
wstring: Remove the ability to put wstrings in hash_map<>s.

(On Windows, where wstring==string16, either will still work.)

BUG=23581

Review URL: http://codereview.chromium.org/7031017

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@85558 0039d316-1c4b-4281-b951-d872f2087c98

ropik/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,gavinp/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,ropik/chromium,yitian134/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,adobe/chromium,ropik/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium