[ios] moved code to use url loading service Load()

Move all calls to UrlLoadingService to use Load().
Added some more factory ctor to UrlLoadParams.

Bug: 907527
Change-Id: I99f0acb5e65e696269c937efcd9da4ce8d548ae3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1505502
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: David Jean <djean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641538}
22 files changed