Plumb timeToNextEffect through players and animation

Source/core/animation/Player.h

Index: Source/core/animation/Player.h
diff --git a/Source/core/animation/Player.h b/Source/core/animation/Player.h
index 84ea0e49967476deeb1fd416a8c4d884f773db6b..22979a6d1233589bd11d968018a981d7e4f41b5c 100644
--- a/Source/core/animation/Player.h
+++ b/Source/core/animation/Player.h
@@ -45,7 +45,18 @@ public:
     static PassRefPtr<Player> create(DocumentTimeline*, TimedItem*);
 
     // Returns whether this player is still current or in effect.
-    bool update();
+    // timeToEffectChange returns:
+    //  -1  - if this player is no longer in effect

[Timothy Loh, 2013/10/18 06:01:27]

Maybe change -1 to std::numeric_limits<double>::infinity() so you can use min to
reduce multiple values? It's also more semantically meaningful.

[shans, 2013/10/21 00:37:57]

Done.

+    //  0   - if this player requires an update on the next frame
+    //  n   - if this player requires an update after 'n' units of time
+    bool update(double& timeToEffectChange);
+
+    inline bool update()

[Timothy Loh, 2013/10/18 06:01:27]

Do we need to keep this version around?

[shans, 2013/10/21 00:37:57]

Yeah. There are a few places where we simply don't care about the result of
timeToEffectChange. It's not cool to put the onus of creating a throwaway
variable on the caller in these cases.

+    {
+        double tmp;

[Timothy Loh, 2013/10/18 06:01:27]

We don't use these sorts of abbreviated variable names. Maybe 'placeholder', but
someone else can probably come up with a better name here.

[shans, 2013/10/21 00:37:57]

Changed to 'unused'

+        return update(tmp);
+    }
+
     void cancel();
     double currentTime() const;
     void setCurrentTime(double);