[Android] Enable remote debugging after rebase to M39

Adjust classes according upstream changes of DevToolsManagerDelegate
and DevToolsHttpHandlerDelegate.
Besides, hardcode webkit revision to generate remote frontend url
due to https://code.google.com/p/chromium/issues/detail?id=425912
> In any case, if we go with the hook approach we've been discussing in crosswalk-project/chromium-crosswalk#199 we could just set the revision we want in DEPS.xwalk, right?

True, I will go with this one.