Add additive animation support for CSS property translate

third_party/WebKit/Source/platform/Length.h

Index: third_party/WebKit/Source/platform/Length.h
diff --git a/third_party/WebKit/Source/platform/Length.h b/third_party/WebKit/Source/platform/Length.h
index 30c7d6349ca618e7d88733f60c1606aed66ab456..fe085d99c73fb8d2e727d30a62c347a21d643d2d 100644
--- a/third_party/WebKit/Source/platform/Length.h
+++ b/third_party/WebKit/Source/platform/Length.h
@@ -160,11 +160,18 @@ public:
         return getIntValue();
     }
 
+    float pixels() const
+    {
+        ASSERT(type() == Fixed);
+        return getFloatValue();
+    }
+
     float percent() const
     {
         ASSERT(type() == Percent);
         return getFloatValue();
     }
+
     PixelsAndPercent pixelsAndPercent() const;
 
     CalculationValue& calculationValue() const;