Make the web-animations engine use the passed in blink::WebFrameTime values.

public/platform/WebFrameTime.h

Index: public/platform/WebFrameTime.h
diff --git a/public/platform/WebFrameTime.h b/public/platform/WebFrameTime.h
index 1050291c23f3db6177e84cc5bb3a7aa9feec7b15..b344149d1441de86b2188f31d73f1d9d03c949a0 100644
--- a/public/platform/WebFrameTime.h
+++ b/public/platform/WebFrameTime.h
@@ -36,6 +36,22 @@
 namespace blink {
 
 struct WebFrameTime {
+    // Before C++0x we can't define a static const member with floating point
+    // value so are forced to use a function here. When we can use C++0x
+    // replace this with (for better performance);
+    //  static constexpr double Undefined() { return -1.0 };
+    inline static const double Undefined()
+    {
+        return -1;
+    }
+
+    WebFrameTime()
+        : lastFrameTime(Undefined())
+        , renderDeadline(Undefined())
+        , displayFrameTime(Undefined())
+        , predictedNextDisplayFrameTime(Undefined())
+    { }
+
     WebFrameTime(double lastFrameTime, double renderDeadline, double displayFrameTime, double predictedNextDisplayFrameTime)
         : lastFrameTime(lastFrameTime)
         , renderDeadline(renderDeadline)
@@ -43,6 +59,15 @@ struct WebFrameTime {
         , predictedNextDisplayFrameTime(predictedNextDisplayFrameTime)
     { }
 
+    bool isNull() const
+    {
+        return (
+            lastFrameTime == Undefined()
+            && renderDeadline == Undefined()
+            && displayFrameTime == Undefined()
+            && predictedNextDisplayFrameTime == Undefined());
+    }
+
     // FIXME(mithro): Upgrade the time in CLOCK_MONOTONIC values to use a
     // TimeTick like class rather than a bare double.