Use unique_ptr for BrowserWithTestWindowTest::CreateBrowserWindow().

Bug: 948877
Change-Id: If2dee43b18c4e537ff25433918afae9b35268970
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1564563
Commit-Queue: Alan Screen <awscreen@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652228}
19 files changed