[ChromeDriver] Return debugging port in capabilities

Add a new entry chrome.debuggerAddress in the capabilities returned from
InitSession command. It contains the hostname and port to reach Chrome's
remote debugging port.

Also removed an unused constructor in struct BrowserInfo.

TBR=crouleau@chromium.org

Bug: 865982, chromedriver:2379
Change-Id: Ic36c08eb7fe42b27fa1ba796ee10c511d76ef804
Reviewed-on: https://chromium-review.googlesource.com/1133421
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#574640}(cherry picked from commit 403b2e9ab1b7ebe8d476a38052fc8a242b9f7d1a)
Reviewed-on: https://chromium-review.googlesource.com/1144063
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#728}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
4 files changed