Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

Source/core/css/StyleSheetContents.cpp

Index: Source/core/css/StyleSheetContents.cpp
diff --git a/Source/core/css/StyleSheetContents.cpp b/Source/core/css/StyleSheetContents.cpp
index 54be1d2e116d66b66ba9db64ef8902616d637fd1..77d215fd242895905f68e9e48576c8207d957c67 100644
--- a/Source/core/css/StyleSheetContents.cpp
+++ b/Source/core/css/StyleSheetContents.cpp
@@ -47,7 +47,7 @@ unsigned StyleSheetContents::estimatedSizeInBytes() const
     // The assumption is that nearly all of of them are atomic and would exist anyway.
     unsigned size = sizeof(*this);
 
-    // FIXME: This ignores the children of media and region rules.
+    // FIXME: This ignores the children of media rules.
     // Most rules are StyleRules.
     size += ruleCount() * StyleRule::averageSizeInBytes();
 
@@ -481,10 +481,6 @@ static bool childRulesHaveFailedOrCanceledSubresources(const Vector<RefPtr<Style
             if (childRulesHaveFailedOrCanceledSubresources(toStyleRuleMedia(rule)->childRules()))
                 return true;
             break;
-        case StyleRuleBase::Region:
-            if (childRulesHaveFailedOrCanceledSubresources(toStyleRuleRegion(rule)->childRules()))
-                return true;
-            break;
         case StyleRuleBase::Import:
             ASSERT_NOT_REACHED();
         case StyleRuleBase::Page: