Gracefully handle zero duration curves in CCActiveAnimation

cc/test/CCAnimationTestCommon.h

Index: cc/test/CCAnimationTestCommon.h
diff --git a/cc/test/CCAnimationTestCommon.h b/cc/test/CCAnimationTestCommon.h
index 6995f77a8e0d6cb2cab5ea34ff9bdbf24f5e964f..6ebf199e97feb69def061304b04fee60152ccf93 100644
--- a/cc/test/CCAnimationTestCommon.h
+++ b/cc/test/CCAnimationTestCommon.h
@@ -22,11 +22,15 @@ namespace WebKitTests {
 class FakeFloatAnimationCurve : public cc::CCFloatAnimationCurve {
 public:
     FakeFloatAnimationCurve();
+    explicit FakeFloatAnimationCurve(double duration);
     virtual ~FakeFloatAnimationCurve();
 
     virtual double duration() const OVERRIDE;
     virtual float getValue(double now) const OVERRIDE;
     virtual PassOwnPtr<cc::CCAnimationCurve> clone() const OVERRIDE;
+
+private:
+    double m_duration;
 };
 
 class FakeTransformTransition : public cc::CCTransformAnimationCurve {