json_schema_compiler: make the preview server retrieve the code HTML via XHR rather than iframes. It's a bit neater, and fixes the back button problem.
json_schema_compiler: make the preview server retrieve the code HTML via XHR
rather than iframes. It's a bit neater, and fixes the back button problem.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9466045

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@123829 0039d316-1c4b-4281-b951-d872f2087c98

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