Skip creating NetworkChangeNotifier if NetworkService is running in process

net::NetworkChangeNotifier's constructor checks to see that it is
the only instance in the process. If NetworkService is running in
process (which happens for some browser tests), an
NetworkChangeNotifier would have been created. If so, skip creating
a second net::NetworkChangeNotifier in NetworkService.

This CL disables the tests for OS_FUCHSIA which doesn't yet have a
platform NetworkChangeNotifier implementation.

Bug: 776599, 754709
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: Ia6fa294be7a6d1adb2119aa6d8743fa780216350
Reviewed-on: https://chromium-review.googlesource.com/731244
Commit-Queue: Helen Li <[email protected]>
Reviewed-by: Matt Menke <[email protected]>
Cr-Commit-Position: refs/heads/master@{#510781}
4 files changed