[android_webview] Fix android_webview_resources dependency.
We need the android_webview_resources stamp file to be a dependency
of the R_file_stamp to force the resources to be generated before
we invoke AAPT on them.
LOCAL_ADDITIONAL_DEPENDENCIES was insufficient since that would
force generating the resources at a later stage.
BUG=393825
R=torne@chromium.org
Review URL: https://codereview.chromium.org/
432753002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@286762 0039d316-1c4b-4281-b951-d872f2087c98