Move interpolated Length unit types out of InterpolableValue into NonInterpolableValue

Source/core/animation/InterpolationType.h

Index: Source/core/animation/InterpolationType.h
diff --git a/Source/core/animation/InterpolationType.h b/Source/core/animation/InterpolationType.h
index b32232d5f5d09eeec32fa15a382579b7021a4e96..906ef9f9bb95768b39d4bbfcf60b742789c0c8b2 100644
--- a/Source/core/animation/InterpolationType.h
+++ b/Source/core/animation/InterpolationType.h
@@ -39,7 +39,11 @@ public:
         OwnPtrWillBeRawPtr<InterpolationValue> endValue = maybeConvertSingle(endKeyframe, state, conversionCheckers);
         if (!endValue)
             return nullptr;
-        return PairwisePrimitiveInterpolation::create(*this, startValue->m_interpolableValue.release(), endValue->m_interpolableValue.release(), startValue->m_nonInterpolableValue.release());
+        return PairwisePrimitiveInterpolation::create(
+            *this,
+            startValue->m_interpolableValue.release(),
+            endValue->m_interpolableValue.release(),
+            mergeNonInterpolableValues(startValue->nonInterpolableValue(), endValue->nonInterpolableValue()));
     }
 
     virtual PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertSingle(const CSSPropertySpecificKeyframe& keyframe, const StyleResolverState* state, ConversionCheckers& conversionCheckers) const
@@ -56,9 +60,15 @@ public:
 
     virtual PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertUnderlyingValue(const StyleResolverState&) const = 0;
 
+    virtual PassRefPtrWillBeRawPtr<NonInterpolableValue> mergeNonInterpolableValues(const NonInterpolableValue* a, const NonInterpolableValue* b) const

[dstockwell, 2015/08/31 06:44:26]

comment, what does it mean to merge these?

[alancutter (OOO until 2018), 2015/09/01 00:26:00]

Added comment. Changed default implementation to assert and return nullptr as I
can't actually think of a situation where we'd simply take the RHS.

+    {
+        // Remove const for ref counting.
+        return const_cast<NonInterpolableValue*>(b);
+    }
+
     virtual void apply(const InterpolableValue&, const NonInterpolableValue*, StyleResolverState&) const = 0;
 
-    // Implement reference equality checking via pointer equality checking as these are singletons
+    // Implement reference equality checking via pointer equality checking as these are singletons.
     bool operator==(const InterpolationType& other) const { return this == &other; }
     bool operator!=(const InterpolationType& other) const { return this != &other; }