Merge 125702 - [chromium] Must account for empty transformation lists when checking for big rotatio…

Merge 125702 - [chromium] Must account for empty transformation lists when checking for big rotations.
https://bugs.webkit.org/show_bug.cgi?id=93975

Reviewed by James Robinson.

Source/WebCore:

AnimationTranslationUtil.cpp is supposed to reject large rotations
(>= 180 degrees between keyframes). The current code assumes that if
the lists of transforms at two consecutive keyframes do not match
(i.e., are different types), then do not need to reject. The rationale
is that we will revert to matrix blending -- we will collapse the lists
of transform operations to matrices at each keyframe and blend those.
Unfortunately, this is not true if a list is empty. It can be the case
that we transition from no transform to a rotation about the z axis of
360 degrees. In this case, the first list of transform operations will
be empty and the second will have a single rotation of 360 degrees. An
empty list should be treated as a rotation of zero degrees.

Unit tested in: GraphicsLayerChromiumTest.createTransformAnimationWithBigRotationAndEmptyTransformOperationList

* platform/graphics/chromium/AnimationTranslationUtil.cpp:
(WebCore::causesRotationOfAtLeast180Degrees):

Source/WebKit/chromium:

Adds a test to check that creating an animation with a big (> 180
degree) rotation, where the transform operations list in the 1st
keyframe is empty fails as expected.

* tests/AnimationTranslationUtilTest.cpp:
(WebKit::TEST):
(WebKit):


TBR=vollick@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=125842