Investigate whether it's the number or just the rapidity that causes this.

It seems that the cause is rapidly opening/closes the dialog. Also seems to be a chrome issue, investigating on the root of this crash.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a676fff41c35a3e1c420074d5fa4c9fa9dc8faef

commit a676fff41c35a3e1c420074d5fa4c9fa9dc8faef
Author: jimmy <jimmyxgong@chromium.org>
Date: Wed Oct 10 21:08:23 2018

Reset MdnsHostLocator when finding hosts

- This fixes a race condition crash when rapidly opening and closing the Add
  Share dialog.
- The crash occurs because |mdns_client_| runs into a race condition in
  which an older state of |mdns_client_| will attempt to create
  Transactions from an invalid state. Previously, |mdns_client_| gets
  reassigned to a new object at every new Add Share dialog. Because Host
  Locators run asynchronously, |mdns_client| will attempt to create all its
  Transactions. This means that if a user closes the Add Share dialog
  and reopens it, an older state of |mdns_client| will continue to
  attempt to create Transactions despite being in an invalid state.
- The fix is to prevent an invalid |mdns_client| from accessing any old
  data by resetting MdnsHostLocator at the start of a new Add Share
  dialog.

Bug:  chromium:892287 
Change-Id: Ie054eadc6cdf83553b31a9cae86df54ea9a986c8
Reviewed-on: https://chromium-review.googlesource.com/c/1272807
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: Zentaro Kavanagh <zentaro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598502}
[modify] https://crrev.com/a676fff41c35a3e1c420074d5fa4c9fa9dc8faef/chrome/browser/chromeos/smb_client/discovery/mdns_host_locator.cc

Workaround landed with CL in #5. Moving to 72 to consider longer term fix

Dropping to P2 now that the workaround is in place.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6405d08c931487287b11d654f4681515bd6051b7

commit 6405d08c931487287b11d654f4681515bd6051b7
Author: Jimmy Gong <jimmyxgong@google.com>
Date: Tue Nov 27 23:27:22 2018

Add discovery and share callback vectors to SmbShareFinder

- Adds vectors for both discovery and share callbacks.
- Solves the race condition in which multiple
  dialogs of "Add Smb Share" would use a shared instance of each
  HostLocator.
- If a SmbShareFinder::GatherSharesInNetwork call comes in when one is
  already running, the callbacks are stored and run when the original
  GatherSharesInNetwork call finishes.
- Adds additional unit test to reflect on the changes.

Bug:  chromium:892287 
Test: end-to-end
Change-Id: I9551532dc08fd9338803786bdd89f0398f4ce7db
Reviewed-on: https://chromium-review.googlesource.com/c/1336435
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: jimmy gong <jimmyxgong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611409}
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chrome/browser/chromeos/smb_client/discovery/in_memory_host_locator.cc
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chrome/browser/chromeos/smb_client/discovery/in_memory_host_locator.h
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chrome/browser/chromeos/smb_client/discovery/network_scanner.cc
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chrome/browser/chromeos/smb_client/discovery/network_scanner.h
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chrome/browser/chromeos/smb_client/smb_share_finder.cc
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chrome/browser/chromeos/smb_client/smb_share_finder.h
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chrome/browser/chromeos/smb_client/smb_share_finder_unittest.cc
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chromeos/dbus/fake_smb_provider_client.cc
[modify] https://crrev.com/6405d08c931487287b11d654f4681515bd6051b7/chromeos/dbus/fake_smb_provider_client.h

Verified and observed no crash on open/close of Add File Share dialog. (Settings> Network file shares> Add File Share) 

Google Chrome(72.0.3626.30,11316.36.0) 

Hence, marking the issue as verified.