Specs: Some notes on combining simultaneous animations of the same property

sky/specs/animation.md

Index: sky/specs/animation.md
diff --git a/sky/specs/animation.md b/sky/specs/animation.md
index e101bb4f46b265905c32ff9ea53310b7e958eceb..af6bd3efeb05bc79e8a4cac129814e00342642f4 100644
--- a/sky/specs/animation.md
+++ b/sky/specs/animation.md
@@ -1,6 +1,9 @@
 Animation API
 =============
 
+(This is very incomplete, because it's all expected to be in the
+framework, not the platform.)
+
 ```javascript
 
 dictionary EasingFunctionSettings {
@@ -16,6 +19,14 @@ abstract class EasingFunction {
     // (but it could in practice go outside this range, e.g. for
     // animation styles that overreach then come back)
 }
+```
 
 
-```
+If you want to have two animations simultaneously, e.g. two
+transforms, then you can add to the RenderNode's overrideStyles a
+StyleValue that combines other StyleValues, e.g. a
+"TransformStyleValueCombinerStyleValue", and then add to it the
+regular animated StyleValues, e.g. multiple
+"AnimatedTransformStyleValue" objects. A framework API could make
+setting all that up easy, given the right underlying StyleValue
+classes.