Add support for font-weight: lighter for web fonts

Source/core/css/FontFace.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 419 matching lines @@
             break;
         case CSSValue500:
             traitsMask |= FontWeight500Mask;
             break;
         case CSSValue300:
             traitsMask |= FontWeight300Mask;
             break;
         case CSSValue200:
             traitsMask |= FontWeight200Mask;
             break;
+        case CSSValueLighter:
         case CSSValue100:
             traitsMask |= FontWeight100Mask;
             break;
         default:
+            ASSERT_NOT_REACHED();
             break;
         }
     } else {
         traitsMask |= FontWeight400Mask;
     }
 
     if (RefPtr<CSSValue> fontVariant = m_variant) {
         // font-variant descriptor can be a value list.
         if (fontVariant->isPrimitiveValue()) {
             RefPtr<CSSValueList> list = CSSValueList::createCommaSeparated();
@@ skipping 77 matching lines @@
         unsigned numRanges = rangeList->length();
         for (unsigned i = 0; i < numRanges; i++) {
             CSSUnicodeRangeValue* range = toCSSUnicodeRangeValue(rangeList->itemWithoutBoundsCheck(i));
             cssFontFace->ranges().add(range->from(), range->to());
         }
     }
     return cssFontFace;
 }
 
 } // namespace WebCore