Telemetry: Don't expose ListInspectableContexts from DevtoolsClientBackend.

Telemetry: Don't expose ListInspectableContexts from DevtoolsClientBackend.

This is a task left over from Issue 423954. I made the method private, and
added public methods to give InspectorBackend the same functionality.

I removed the method ListInspectableContexts from IosBrowserBackend and
ChromeBrowserBackend, since its never used.

BUG=423954, 460625
Committed: https://crrev.com/dc302039d5febcc8f97e9848ab2be4f93ed75f63
Cr-Commit-Position: refs/heads/master@{#321014}

[erikchen, 2015-03-13 18:20:25]

erikchen@chromium.org changed reviewers:
+ dtu@chromium.org

[erikchen, 2015-03-13 18:20:26]

dtu: Please review.

https://codereview.chromium.org/1001393002/diff/1/tools/telemetry/telemetry/c...
File
tools/telemetry/telemetry/core/backends/chrome_inspector/devtools_client_backend.py
(right):

https://codereview.chromium.org/1001393002/diff/1/tools/telemetry/telemetry/c...
tools/telemetry/telemetry/core/backends/chrome_inspector/devtools_client_backend.py:147:
def GetUrl(self, tab_id):
It's unexpected for accessing a property to throw an exception. It's also
unexpected for accessing a property to synchronously send a network request.
This is why I made a method instead of a property.

"url" is still a property on Tab and InspectorBackend, but that's a task for a
separate CL.

[dtu, 2015-03-17 21:39:20]

lgtm

[erikchen, 2015-03-17 21:42:06]

The CQ bit was checked by erikchen@chromium.org

[commit-bot: I haz the power, 2015-03-17 21:42:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1001393002/1

[commit-bot: I haz the power, 2015-03-17 23:57:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-17 23:57:54]

Patchset 1 (id:??) landed as
https://crrev.com/dc302039d5febcc8f97e9848ab2be4f93ed75f63
Cr-Commit-Position: refs/heads/master@{#321014}