GitLab

This CL:

1) Replaced AwContentsIoThreadClient with AwContentsIoThreadClientImpl
2) Replaced InputStream with InputStreamImpl
3) Replaced AwWebResourceResponse with AwWebResourceResponseImpl, and
   moved implementation into browser/net/.

Replacing them due to the merge of native/ and browser/

BUG=716604

Review-Url: https://codereview.chromium.org/2889193004
Cr-Commit-Position: refs/heads/master@{#473769}