Web Animations CSS: Fix crash when animating viewport units

Source/core/animation/AnimatableLength.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 79 matching lines @@
     return toCSSPrimitiveValue(range)->convertToLength<AnyConversion>(conversionData);
 }
 
 PassRefPtr<AnimatableValue> AnimatableLength::interpolateTo(const AnimatableValue* value, double fraction) const
 {
     const AnimatableLength* length = toAnimatableLength(value);
     NumberUnitType type = commonUnitType(length);
     if (type != UnitTypeCalc)
         return AnimatableLength::create(blend(m_number, length->m_number, fraction), type);
 
+    // FIXME(crbug.com/168840): Support for viewport units in calc needs to be added before we can blend them with other units.
+    if (isViewportUnit() || length->isViewportUnit())
+        return defaultInterpolateTo(this, value, fraction);
+
     return AnimatableLength::create(scale(1 - fraction).get(), length->scale(fraction).get());
 }
 
 PassRefPtr<AnimatableValue> AnimatableLength::addWith(const AnimatableValue* value) const
 {
     // Optimization for adding with 0.
     if (isUnitlessZero())
         return takeConstRef(value);
 
     const AnimatableLength* length = toAnimatableLength(value);
@@ skipping 118 matching lines @@
     case UnitTypeViewportMax:
         return CSSPrimitiveValue::CSS_VMAX;
     case UnitTypeCalc:
         return CSSPrimitiveValue::CSS_UNKNOWN;
     }
     ASSERT_NOT_REACHED();
     return CSSPrimitiveValue::CSS_UNKNOWN;
 }
 
 } // namespace WebCore