Use IOSImageDataFetcherWrapper for favicon

Use IOSImageDataFetcher instead of ImageDataFetcher for downloading the favicon
on iOS. This allows the download to be done in the favicon driver instead of the
WebState.
The favicon needs the http response code for optimization (if the favicon does
not exist we try to download it only once).

BUG=683918

Review-Url: https://codereview.chromium.org/2677993002
Cr-Original-Commit-Position: refs/heads/master@{#450317}
Committed: https://chromium.googlesource.com/chromium/src/+/911c2949fcb7a8362449e8af1d60bbb93d3cfab5
Review-Url: https://codereview.chromium.org/2677993002
Cr-Commit-Position: refs/heads/master@{#450345}
17 files changed