Make 'web_view_browsertest.cc' (almost) BrowserPlugin-free

The BrowserPlugin related tests in the file were to test features that
affect BP-based GuestViews; this only includes MimeHandlerViewGuest.

This CL moves one more such test to
'chrome_mime_handler_view_browsertest.cc'. This also involves adapting
the test such that it creates a MimeHandlerViewGuest instead of
WebViewGuest based on BrowserPlugin.

The last remaining test in 'web_view_browsertest.cc' will be removed and
adapted in a followup CL (to make sure the process is easily reversible
in case the new tests end up having issues on bots).

Bug: 553069, 330264
Change-Id: Iaa7ba33189ecb8b23e8489dab8e9b2b5e378a9be
Reviewed-on: https://chromium-review.googlesource.com/1217147
Reviewed-by: James MacLean <wjmaclean@chromium.org>
Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
Commit-Queue: Ehsan Karamad <ekaramad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590372}
4 files changed