Handle font-weigths with 'bolder' or 'lighter' values in @font-face rules

Source/core/css/FontFace.cpp

Index: Source/core/css/FontFace.cpp
diff --git a/Source/core/css/FontFace.cpp b/Source/core/css/FontFace.cpp
index a6250bab725d18e724d209986bf554966694d37b..6d8dec5b283684a440ea779e1a254b3bc1a59571 100644
--- a/Source/core/css/FontFace.cpp
+++ b/Source/core/css/FontFace.cpp
@@ -443,10 +443,14 @@ FontTraits FontFace::traits() const
         case CSSValue200:
             weight = FontWeight200;
             break;
-        case CSSValueLighter:
         case CSSValue100:
             weight = FontWeight100;
             break;
+        // Although 'lighter' and 'bolder' are valid keywords for font-weights, they are invalid
+        // inside font-face rules so they are ignored. Reference: http://www.w3.org/TR/css3-fonts/#descdef-font-weight.
+        case CSSValueLighter:
+        case CSSValueBolder:
+            break;
         default:
             ASSERT_NOT_REACHED();
             break;