Update targetSdkVersion to 20.

Applications targeting this or a later release will get these new changes
in behavior:
  - AlertDialog might not have a default background if the theme does not
    specify one.

BUG=393019
TBR=stgao@chromium.org,blundell@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/402613008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284131 0039d316-1c4b-4281-b951-d872f2087c98
Get rid of the rest of CreateStringValue

BUG=160586

Review URL: https://codereview.chromium.org/388963002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284201 0039d316-1c4b-4281-b951-d872f2087c98