feat($http): add support for timeout promises

[dbinit]

If the timeout argument is a promise, abort the request when it is resolved.
Implemented by adding support to $httpBackend service and $httpBackend mock service.

This is yet another approach to the $http cancel issue (see #2452 and #2523). Obviously there is still a lack of consensus on how to handle it (see kriskowal/q#64), so I propose this as an alternative.

Closes#1159

[IgorMinar]

I like this quite a bit since unlike all the other attempts it doesn't try to introduce an explicit bi-directional communication between deferred and a promise.

Can you add the missing higher level test please? I'll then highlight this PR one angular-dev for api review. I'm quite hopeful about this PR this time around :)

[dbinit]

Excellent!

I'll get some more tests in there ASAP. Looks like I'll have to add timeouts to the mock version of $httpBackend, but it shouldn't take long.

[dbinit]

Ok, tests added.

I did my best to follow the style/spirit of existing code with this (while keeping changes minimal). Let me know if there are any issues there.

[dbinit]

Hi @IgorMinar. Any update on this?

[petebacondarwin]

• Contributor signed CLA now or in the past (if you just signed, leave a comment here with your real name)
• Feature is focused on a core value of the framework
• PR is approved by 2+ senior team members and no committer is blocking the change
• API is compatible with existing Angular apis and relevant standards (if applicable)
• Intentional breaking change
  • Approved by 2+ senior team members
  • The breaking change is documented (including migration steps)
• PR contains unit tests
• PR contains documentation update
• PR passes all tests on Travis (sanity)
• PR passes all tests on ci.angularjs.org (cross-browser compatibility)
• PR is rebased against recent master
• PR is squashed into one commit per logical change
• PR's commit messages are descriptive and allows us to autogenerate release notes (required commit message format)
• All changes requested in review have been implemented

[petebacondarwin]

I'll ping the dev team on this.

[aaronleesmith]

Waiting for this to go through to build a feature. Any update?

[vojtajina]

LGTM.

[vojtajina]

🚢 it

[IgorMinar]

Landed as 9f4f593!

Thanks so much for being patient with us.

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