Run the expected output for RefTests with virtual test suite arguments.

Currently we're always using an empty argument list (oops), because
we look up the arguments with the test name after removing the virtual
test suite part from the test name.

R=dpranke@chromium.org
BUG=367315, 368008

Review URL: https://codereview.chromium.org/257843006

git-svn-id: svn://svn.chromium.org/blink/trunk@172820 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Web Animations: Allow timing function inputs outside the range [0, 1]

FOR LINEAR TIMING FUNCTIONS
the timing function is naturally extended so that output continues to equal input

FOR STEP FUNCTIONS
the step is clamped to the range [0, 1]

FOR BEZIERS
End-point gradients are used to calculate timing function results outside the range [0, 1].

There are three possibilities for the gradient at each end:
(1) the closest control point is not horizontally coincident
    with regard to (0, 0) or (1, 1). In this case the line 
    between the end point and the control point is tangent to
    the bezier at the end point.
(2) the closest control point is coincident with the end 
    point. In this case the line between the end point and 
    the far control point is tangent to the bezier at the end
    point.
(3) the closest control point is horizontally coincident with 
    the end point, but vertically distinct. In this case the 
    gradient at the end point is Infinite. However, this 
    causes issues when interpolating. As a result, we break 
    down to a simple case of 0 gradient under these 
    conditions.

Review URL: https://codereview.chromium.org/238573002

git-svn-id: svn://svn.chromium.org/blink/trunk@172821 bbb929c8-8fbe-4397-9dbb-9b2b20218538