This allow finer grain control over what is rebuilt.
Also, since we have approval over the generated header file name,
it greatly simplifies both the generator and also all the gyp files
as they no longer need to list the header file and keep in sync with the
java file, so the process now is as simple as adding a single java file
to the sources.
BUG=137069
TEST=build on android
Review URL: https://chromiumcodereview.appspot.com/10798010
git-svn-id: http://src.chromium.org/svn/trunk/src/build@147515 4ff67af0-8c30-449e-8e8b-ad334ec8d88c