Replace Platform::Current() with TestingPlatformSupport to call GetURLLoaderMockFactory.

This patch is for replacing Platform::Current()->GetURLLoaderMockFactory()
calls with TestingPlatformSupport's GetURLLoaderMockFactory()
under "third_party/blink/renderer/core/"

Bug: 751425
Change-Id: Ifd944b5a5ce743f281aa42b2ef92d917fcdeeeb0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1567711
Commit-Queue: DongJun Kim <djmix.kim@samsung.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685442}
28 files changed