Switch WebURLLoaderMock::ServeAsynchronousRequest to delegate all calls.

So blink unit tests can precicely control the didReceiveData and
didFinishLoading callbacks to simulate network requests coming in
at specific times we switch to using the rest of the newly
expanded API of WebURLLoaderTestDelegate which now can proxy all
the related callbacks for network requests.

Now blink unit tests can buffer the data and delay the response
and finishedLoading callbacks to create specific timing situations
like having certain stylesheets return before others or running
script before sheets have loaded.

R=dcheng@chromium.org
BUG=521692

Review URL: https://codereview.chromium.org/1313473002

Cr-Commit-Position: refs/heads/master@{#345333}
1 file changed