Devtools Animations: Add cubic bezier easing editor for animations

Source/devtools/front_end/elements/BezierUI.js

Index: Source/devtools/front_end/elements/BezierUI.js
diff --git a/Source/devtools/front_end/elements/BezierUI.js b/Source/devtools/front_end/elements/BezierUI.js
index 2a9b716fd317eb9e730c768dfb4878a302543c40..5964f4ed59cd7b28c6d8046c4de5bd93e6e58d90 100644
--- a/Source/devtools/front_end/elements/BezierUI.js
+++ b/Source/devtools/front_end/elements/BezierUI.js
@@ -117,6 +117,9 @@ WebInspector.BezierUI.drawVelocityChart = function(bezier, path, width)
         var slope = (current.y - prev.y) / (current.x - prev.x);
         var weightedX = prev.x * (1 - t) + current.x * t;
         slope = Math.tanh(slope / 1.5); // Normalise slope
+        // TODO(samli): Workaround for v8 bug https://code.google.com/p/v8/issues/detail?id=3495
+        if (isNaN(slope))
+            slope = 1;
         pathBuilder = pathBuilder.concat(["L", (weightedX * width).toFixed(2), (height - slope * height).toFixed(2) ]);
         prev = current;
     }