fix(httpBackend): should not read response data when request is aborted

When a request is aborted, it makes no sense to read the response headers or text.
Also in IE9, trying to read data (either response headers or text) from an aborted request
throws an Error c00c023f.

Fixes #4913
Closes #4940
fix($compile): secure form[action] & iframe[srcdoc]

Require bindings to form[action] to be $sce.RESOURCE_URL and bindings to
iframe[srcdoc] to be $sce.HTML

Closes #4927
Closes #4933
Merge branch 'master' of https://github.com/angular/angular.js