bluetooth: Add NetworkError for Bluetooth on browser side

bluetooth: Add NetworkError for Bluetooth on browser side

Return the NetworkError if the connectGATT fails.

This is the second of two patches to implement NetworkError:
  [1] https://codereview.chromium.org/1124973003
  [2] This patch.

BUG=484779
Committed: https://crrev.com/71fd6178f81b1a40d201da5f8144354e5e92bd71
Cr-Commit-Position: refs/heads/master@{#329512}

[scheib, 2015-05-05 22:34:13]

scheib@chromium.org changed reviewers:
+ scheib@chromium.org

[scheib, 2015-05-05 22:34:14]

Please add a reference note to
https://github.com/WebBluetoothChrome/web-bluetooth

[scheib, 2015-05-05 22:38:12]

LGTM

[ortuno, 2015-05-12 21:23:03]

The CQ bit was checked by ortuno@chromium.org

[ortuno, 2015-05-12 21:23:03]

The patchset sent to the CQ was uploaded after l-g-t-m from scheib@chromium.org
Link to the patchset: https://codereview.chromium.org/1118053003/#ps40001
(title: "Remove from bluetooth_dispatcher_host so that we can commit")

[commit-bot: I haz the power, 2015-05-12 21:24:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1118053003/40001

[commit-bot: I haz the power, 2015-05-12 22:25:14]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-05-12 22:26:02]

Patchset 3 (id:??) landed as
https://crrev.com/71fd6178f81b1a40d201da5f8144354e5e92bd71
Cr-Commit-Position: refs/heads/master@{#329512}