CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/html/canvas/CanvasFontCache.cpp

Index: Source/core/html/canvas/CanvasFontCache.cpp
diff --git a/Source/core/html/canvas/CanvasFontCache.cpp b/Source/core/html/canvas/CanvasFontCache.cpp
index 99d66a3d143059acd5c9d59b7ffdef13e2994bd7..992df041e5d88c4bd5caa8880172947415f095be 100644
--- a/Source/core/html/canvas/CanvasFontCache.cpp
+++ b/Source/core/html/canvas/CanvasFontCache.cpp
@@ -97,7 +97,7 @@ MutableStylePropertySet* CanvasFontCache::parseFont(const String& fontString)
             return nullptr;
         // According to http://lists.w3.org/Archives/Public/public-html/2009Jul/0947.html,
         // the "inherit" and "initial" values must be ignored.
-        NullableCSSValue fontValue = parsedStyle->getPropertyCSSValue(CSSPropertyFontSize);
+        const NullableCSSValue& fontValue = parsedStyle->getPropertyCSSValue(CSSPropertyFontSize);
         if (fontValue && (fontValue->isInitialValue() || fontValue->isInheritedValue()))
             return nullptr;
         m_fetchedFonts.add(fontString, parsedStyle);