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Doesn't fix the original issue of notifications failing after reconnect
https://crbug.com/680099 correctly.

Introduces new issue:
startCharacteristicNotifications returns 'Operation failed' after disconnect
https://crbug.com/719581

This reverts commit db614933.
originally from https://codereview.chromium.org/2625013003/

TBR=ortuno@chromium.org,rkc@google.com,scheib@chromium.org,perja@opera.com
BUG=680099,719581

Review-Url: https://codereview.chromium.org/2888663002
Cr-Commit-Position: refs/heads/master@{#472290}