Android WebView: change how the SDK jar is found.
Setting android_sdk has unintended consequences which have recently
broken the build, but we still need to be able to point to the sdk
jarfile for now until this dependency has been solved for real; use the
newly introduced android_sdk_jar variable from r188737 to specify this
and set android_sdk to a harmless but invalid value rather than a make
variable expansion.
BUG=
Review URL: https://codereview.chromium.org/
12917006
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@188747 0039d316-1c4b-4281-b951-d872f2087c98