[CSS Grid Layout] Use CSS_FR for flexible lengths instead of CSS_DIMENSION

Source/core/css/CSSComputedStyleDeclaration.cpp

Index: Source/core/css/CSSComputedStyleDeclaration.cpp
diff --git a/Source/core/css/CSSComputedStyleDeclaration.cpp b/Source/core/css/CSSComputedStyleDeclaration.cpp
index 7ea36ea224f60fe8f2f654855b747ba34485feb1..2fa450b4ffdd1108615acc13b97f885807bd7c0d 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -1001,10 +1001,8 @@ PassRefPtr<CSSValue> CSSComputedStyleDeclaration::valueForFilter(const RenderObj
 
 static PassRefPtr<CSSValue> valueForGridTrackBreadth(const GridLength& trackBreadth, const RenderStyle* style, RenderView* renderView)
 {
-    if (!trackBreadth.isLength()) {
-        String flex = String::number(trackBreadth.flex()) + "fr";
-        return cssValuePool().createValue(flex, CSSPrimitiveValue::CSS_DIMENSION);
-    }
+    if (!trackBreadth.isLength())
+        return cssValuePool().createValue(trackBreadth.flex(), CSSPrimitiveValue::CSS_FR);
 
     const Length& trackBreadthLength = trackBreadth.length();
     if (trackBreadthLength.isAuto())