Mark DOMStringList.contains() as deprecated, add console warning.

Source/bindings/modules/v8/V8BindingForModules.cpp

Index: Source/bindings/modules/v8/V8BindingForModules.cpp
diff --git a/Source/bindings/modules/v8/V8BindingForModules.cpp b/Source/bindings/modules/v8/V8BindingForModules.cpp
index a7740e496db1325c67fd45b0d5699eda8500167d..d0eae41bc1f4adb1d3277fb4583764abc65605ab 100644
--- a/Source/bindings/modules/v8/V8BindingForModules.cpp
+++ b/Source/bindings/modules/v8/V8BindingForModules.cpp
@@ -69,7 +69,7 @@ v8::Local<v8::Value> toV8(const IDBKeyPath& value, v8::Local<v8::Object> creatio
     case IDBKeyPath::StringType:
         return v8String(isolate, value.string());
     case IDBKeyPath::ArrayType:
-        RefPtrWillBeRawPtr<DOMStringList> keyPaths = DOMStringList::create();
+        RefPtrWillBeRawPtr<DOMStringList> keyPaths = DOMStringList::create(DOMStringList::IndexedDB);

[jsbell, 2015/06/12 20:35:38]

Side note: I'm rather surprised to see this here. This was never documented or
specified to be a DOMStringList and Gecko doesn't implement it that way either,
and we have no tests asserting that it is a DOMStringList. This should be a
plain (but possibly frozen?) array.

I'll spin up a separate CL to change it.

         for (Vector<String>::const_iterator it = value.array().begin(); it != value.array().end(); ++it)
             keyPaths->append(*it);
         return toV8(keyPaths.release(), creationContext, isolate);