Strip extraneous AVFoundation and CoreMedia logging
https://bugs.webkit.org/show_bug.cgi?id=136747

Reviewed by Jer Noble.

* Scripts/webkitpy/layout_tests/controllers/single_test_runner.py:
(SingleTestRunner._run_compare_test): Allow the port to specify patterns to strip from stderr.

* Scripts/webkitpy/port/base.py:
(Port.stderr_patterns_to_strip): Base class, empty list

* Scripts/webkitpy/port/driver.py:
(DriverOutput.strip_stderror_patterns): Strip the specified patterns from stderr.

* Scripts/webkitpy/port/ios.py:
(IOSSimulatorPort.stderr_patterns_to_strip): iOS patterns - there are none.

* Scripts/webkitpy/port/mac.py:
(MacPort.stderr_patterns_to_strip): CoreMedia and AVFoundation logging we can ignore.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@173557 268f45cc-cd09-0410-ab3c-d52691b4dbfc