Make font-weight animatable.

Source/core/rendering/style/RenderStyle.cpp

Index: Source/core/rendering/style/RenderStyle.cpp
diff --git a/Source/core/rendering/style/RenderStyle.cpp b/Source/core/rendering/style/RenderStyle.cpp
index 6ea69692f7722e8b7c9626a4bdc111633c79b987..914838bd8366a59792cbe910c95cdc61709297d0 100644
--- a/Source/core/rendering/style/RenderStyle.cpp
+++ b/Source/core/rendering/style/RenderStyle.cpp
@@ -1176,6 +1176,7 @@ const FontDescription& RenderStyle::fontDescription() const { return inherited->
 float RenderStyle::specifiedFontSize() const { return fontDescription().specifiedSize(); }
 float RenderStyle::computedFontSize() const { return fontDescription().computedSize(); }
 int RenderStyle::fontSize() const { return fontDescription().computedPixelSize(); }
+FontWeight RenderStyle::fontWeight() const { return fontDescription().weight(); }
 
 float RenderStyle::wordSpacing() const { return fontDescription().wordSpacing(); }
 float RenderStyle::letterSpacing() const { return fontDescription().letterSpacing(); }
@@ -1248,6 +1249,15 @@ void RenderStyle::setFontSize(float size)
     font().update(currentFontSelector);
 }
 
+void RenderStyle::setFontWeight(FontWeight weight)
+{
+    FontSelector* currentFontSelector = font().fontSelector();
+    FontDescription desc(fontDescription());
+    desc.setWeight(weight);
+    setFontDescription(desc);
+    font().update(currentFontSelector);
+}
+
 void RenderStyle::getShadowExtent(const ShadowList* shadowList, LayoutUnit &top, LayoutUnit &right, LayoutUnit &bottom, LayoutUnit &left) const
 {
     top = 0;