Rename android_build_type to android_webview_build.
Rename android_build_type to android_webview_build.

Rename this gyp variable to something meaningful to better explain what
it actually does.

BUG=184431

Review URL: https://chromiumcodereview.appspot.com/12605007
Patch from Richard Coles <torne@chromium.org>.

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@13916 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh