Bug 1010681 part 1 - Add nsSMILTimedElement::SetIsDisabled for turning off a timed element; r=longsonr

This method is added so that animation elements that fail conditional processing
tests can disable the corresponding timed element. Currently, this handling is
performed by the animation controller which simply skips sampling animations
that fail tests. However, this doesn't provide the correct behavior since
"skipped" animations can still have intervals that trigger syncbase dependencies
etc. Also, we still do milestone samples for "skipped" animations which can
lead to cases where we are in an inconsistent state.

This patch provides a method that will be used in subsequent patches to more
correctly remove the effects of a timed element.

To do this, this patch also factors out some common methods for clearing timing
state that can be shared with the Rewind method.
Bug 1010681 part 2 - Make SVG animation elements call SetIsDisabled on the corresponding timed element; r=longsonr

This patch makes use of the SetIsDisabled method added to nsSMILTimedElement in
the previous patch to "turn off" the associated timed element of an animation
element that has failing conditional processing tests.
Bug 1010681 part 3 - Add mochitest for dynamic changes to conditional processing tests on animation elements; r=longsonr
Bug 1010681 part 4 - Add crashtest for changes to conditional processing tests on animation elements; r=longsonr

Before the changes in this bug, this test used to produce an assertion:

  ABORT: Rewind in the middle of a forwards seek?

This was because for a timed element whose corresponding animation element fails
conditional processing tests, we were still performing milestone samples even
though we were skipping regular samples.
Bug 1010681 part 5 - Remove conditional processing inside animation controller; r=longsonr

Remove the changes to nsSMILAnimationController introduced by bug 619469 now
that we have introduced a more thorough approach to disabling animations that
fail conditional processing tests.
Bug 1010681 part 6 - Remove PassesConditionProcessingTests from SVGAnimationElement; r=longsonr

This method was originally exposed so that the animation compositor could test
if an animation should be skipped when sampling but now that we perform this
testing within the SVGAnimationElement itself it is no longer needed.