Bug 401564 - Test and fix for redirection losing Accept header. r=mcmanus

The test has a redirect where the initial GET request had Accept:
application/json, and ensures that this is also the type of the
redirected request.

The fix is done in the setup of the replicated HttpBaseChannel, where
the previous channel's Accept header is copied to the new one, if it
exists.
Bug 961776 - Add role=key to the event fluffing heuristics. r=roc
Bug 970774 - Add display width/height for track encoder. r=rillian
Bug 975824 - Fix compressed texture checks. r=jgilbert
Bug 975824 - Remove min-version from s3tc and depth conformance tests. r=jgilbert
Bug 975937 - Crash in mozilla::layers::ShaderProgramOGL::Activate(). r=gal