Add a boolean in QuicConnectivityProbingManager to track if probing is active.

We used to rely on the |network_| == kInvalidNetworkHandle check to determine if there's any active probing. This is preparing for probe server preferred address on non-Android platform where network_ may be invalid during active probing. No behavior change.

Bug: 913733
Change-Id: I280da06961b4faac0cf685ed9d994f37db4702f1
Reviewed-on: https://chromium-review.googlesource.com/c/1374792
Commit-Queue: Zhongyi Shi <zhongyi@chromium.org>
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616545}
5 files changed