[Oilpan] Migrate most classes under core/animations to Oilpan heap.

Source/core/animation/animatable/AnimatableDouble.h

Index: Source/core/animation/animatable/AnimatableDouble.h
diff --git a/Source/core/animation/animatable/AnimatableDouble.h b/Source/core/animation/animatable/AnimatableDouble.h
index a37d0c836f14bb488cf2d69937e539d0ecee4bc2..bcc802613a00273cefd9253fd2e58a2887d7d02f 100644
--- a/Source/core/animation/animatable/AnimatableDouble.h
+++ b/Source/core/animation/animatable/AnimatableDouble.h
@@ -45,9 +45,9 @@ public:
         InterpolationIsNonContinuousWithZero,
     };
 
-    static PassRefPtrWillBeRawPtr<AnimatableDouble> create(double number, Constraint constraint = Unconstrained)
+    static AnimatableDouble* create(double number, Constraint constraint = Unconstrained)
     {
-        return adoptRefWillBeNoop(new AnimatableDouble(number, constraint));
+        return new AnimatableDouble(number, constraint);
     }
 
     double toDouble() const { return m_number; }
@@ -55,7 +55,7 @@ public:
     DEFINE_INLINE_VIRTUAL_TRACE() { AnimatableValue::trace(visitor); }
 
 protected:
-    virtual PassRefPtrWillBeRawPtr<AnimatableValue> interpolateTo(const AnimatableValue*, double fraction) const override;
+    virtual AnimatableValue* interpolateTo(const AnimatableValue*, double fraction) const override;
     virtual bool usesDefaultInterpolationWith(const AnimatableValue*) const override;
 
 private: