Creating a helper class for reversing timing functions.

Source/core/animation/CompositorAnimations.h

Index: Source/core/animation/CompositorAnimations.h
diff --git a/Source/core/animation/CompositorAnimations.h b/Source/core/animation/CompositorAnimations.h
index d95196d3a9acc5c26ba155f92282d22097cd5fc1..a21ac367d3c76aa591b6760ee0a0fd1b34ffc51b 100644
--- a/Source/core/animation/CompositorAnimations.h
+++ b/Source/core/animation/CompositorAnimations.h
@@ -39,6 +39,17 @@ namespace WebCore {
 class Element;
 class AnimationEffect;
 
+// Reverse the timing function so that t=0 becomes t=1, t=1 becomes t=0 and
+// t=0.5 stays the same.

[Steve Block, 2013/11/06 06:06:23]

This is a little vague. Given an input timing function and associated start and
end keyframes, we need a timing function such that the behavior with the
keyframes swapped is equivalent to reversing time with the input timing function
and keyframes. This means flipping the timing function about x=0.5 and about
y=0.5.

[mithro-old, 2013/11/07 01:02:37]

Done.

+// FIXME: Remove once the Compositor natively understands reversing time.
+class CompositorAnimationsTimingFunctionReverser {
+public:
+    static PassRefPtr<TimingFunction> reverse(const LinearTimingFunction* timefunc);
+    static PassRefPtr<TimingFunction> reverse(const CubicBezierTimingFunction* timefunc);
+    static PassRefPtr<TimingFunction> reverse(const ChainedTimingFunction* timefunc);

[Steve Block, 2013/11/06 06:06:23]

Do the type-specific reverse methods need to be in this header file?

[mithro-old, 2013/11/07 01:02:37]

Done.

+    static PassRefPtr<TimingFunction> reverse(const TimingFunction* timefunc);
+};
+
 class CompositorAnimations {
 
 public: