Remove FontDescriptionChangeScope, and let FontBuilder partially apply values.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index cf01ec8247ede9efbf6276774aef53b647140f67..91eaf554053ddc8c40b1fdbe52a2efbb257788eb 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -1664,7 +1664,6 @@ void Document::updateDistributionForNodeIfNeeded(Node* node)
 void Document::setupFontBuilder(RenderStyle* documentStyle)
 {
     FontBuilder fontBuilder(*this);
-    fontBuilder.setFontDescription(documentStyle->fontDescription());
     RefPtrWillBeRawPtr<CSSFontSelector> selector = m_styleEngine->fontSelector();
     fontBuilder.createFontForDocument(selector, documentStyle);
 }