Animation: Fix loss of type information when interpolating value of 0

Source/core/animation/LengthBoxStyleInterpolationTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/animation/LengthBoxStyleInterpolation.h"
 
 #include "core/animation/LengthStyleInterpolation.h"
 #include "core/css/CSSPrimitiveValue.h"
 #include "core/css/Rect.h"
@@ skipping 47 matching lines @@
     RefPtrWillBeRawPtr<CSSValue> value = roundTrip(CSSPrimitiveValue::create(rectPx.release()));
     testPrimitiveValue(value, 0, 0, 0, 0, CSSPrimitiveValue::CSS_PX);
 
     RefPtrWillBeRawPtr<Rect> rectEms = Rect::create();
     rectEms->setLeft(CSSPrimitiveValue::create(0, CSSPrimitiveValue::CSS_EMS));
     rectEms->setRight(CSSPrimitiveValue::create(0, CSSPrimitiveValue::CSS_EMS));
     rectEms->setTop(CSSPrimitiveValue::create(0, CSSPrimitiveValue::CSS_EMS));
     rectEms->setBottom(CSSPrimitiveValue::create(0, CSSPrimitiveValue::CSS_EMS));
 
     value = roundTrip(CSSPrimitiveValue::create(rectEms.release()));
-    testPrimitiveValue(value, 0, 0, 0, 0, CSSPrimitiveValue::CSS_PX);
+    testPrimitiveValue(value, 0, 0, 0, 0, CSSPrimitiveValue::CSS_EMS);
 }
 
 TEST_F(AnimationLengthBoxStyleInterpolationTest, SingleUnitBox)
 {
     RefPtrWillBeRawPtr<Rect> rectPx = Rect::create();
     rectPx->setLeft(CSSPrimitiveValue::create(10, CSSPrimitiveValue::CSS_PX));
     rectPx->setRight(CSSPrimitiveValue::create(10, CSSPrimitiveValue::CSS_PX));
     rectPx->setTop(CSSPrimitiveValue::create(10, CSSPrimitiveValue::CSS_PX));
     rectPx->setBottom(CSSPrimitiveValue::create(10, CSSPrimitiveValue::CSS_PX));
 
@@ skipping 34 matching lines @@
     rectPer->setLeft(CSSPrimitiveValue::create(30, CSSPrimitiveValue::CSS_PERCENTAGE));
     rectPer->setRight(CSSPrimitiveValue::create(-30, CSSPrimitiveValue::CSS_PERCENTAGE));
     rectPer->setTop(CSSPrimitiveValue::create(30, CSSPrimitiveValue::CSS_PERCENTAGE));
     rectPer->setBottom(CSSPrimitiveValue::create(-30, CSSPrimitiveValue::CSS_PERCENTAGE));
 
     value = roundTrip(CSSPrimitiveValue::create(rectPer.release()));
     testPrimitiveValue(value, 30, 0, 30, 0, CSSPrimitiveValue::CSS_PERCENTAGE);
 }
 
 }