Add toWebCoreString() / toWebCoreAtomicString() overloads taking a v8::String

Source/bindings/v8/IDBBindingUtilities.cpp

Index: Source/bindings/v8/IDBBindingUtilities.cpp
diff --git a/Source/bindings/v8/IDBBindingUtilities.cpp b/Source/bindings/v8/IDBBindingUtilities.cpp
index 111453eca34027969fb6772a12e51a4a9ae74687..325304b546d257c08b45ae252bb89c70d6265b40 100644
--- a/Source/bindings/v8/IDBBindingUtilities.cpp
+++ b/Source/bindings/v8/IDBBindingUtilities.cpp
@@ -79,7 +79,7 @@ static PassRefPtr<IDBKey> createIDBKeyFromValue(v8::Handle<v8::Value> value, Vec
     if (value->IsNumber() && !std::isnan(value->NumberValue()))
         return IDBKey::createNumber(value->NumberValue());
     if (value->IsString())
-        return IDBKey::createString(toWebCoreString(value));
+        return IDBKey::createString(toWebCoreString(value.As<v8::String>()));
     if (value->IsDate() && !std::isnan(value->NumberValue()))
         return IDBKey::createDate(value->NumberValue());
     if (value->IsArray()) {