Attach a WebBluetooth to the LocalFrame and use it if it's available.

Source/modules/bluetooth/BluetoothSupplement.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BluetoothSupplement_h
+#define BluetoothSupplement_h
+
+#include "core/frame/LocalFrame.h"
+
+namespace blink {
+
+class WebBluetooth;
+
+class BLINK_EXPORT BluetoothSupplement : public NoBaseWillBeGarbageCollected<BluetoothSupplement>, public WillBeHeapSupplement<LocalFrame> {

[scheib, 2015/07/16 01:03:03]

Class comment please to increase readability for those learning the components.
Supplement is sadly missing overview doc explaining what it does, but even with
that we should explain here the concept that when running in a context with a
frame, we obtain a WebBluetooth implementation from that frame that will be able
to show UI on that frame. It would simplify code understanding to have a trace
of the construction flow that causes the supplement to exist there.

[Jeffrey Yasskin, 2015/07/16 22:27:14]

How's this?

[scheib, 2015/07/16 23:04:17]

Great, thank you.

+    WTF_MAKE_NONCOPYABLE(BluetoothSupplement);
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(BluetoothSupplement);
+
+public:
+    static const char* supplementName();
+
+    static void provideTo(LocalFrame&, WebBluetooth*);
+
+    static WebBluetooth* from(LocalFrame*);

[scheib, 2015/07/16 01:03:03]

We only expect users to call from(ScriptState*), right? Consider moving this to
private? 

[Jeffrey Yasskin, 2015/07/16 22:27:14]

I've inlined and deleted it.

+
+    // Returns the WebBluetooth attached to the ScriptState's frame if that exists;
+    // otherwise the Platform's WebBluetooth.
+    static WebBluetooth* from(ScriptState*);
+
+    DECLARE_VIRTUAL_TRACE();
+
+private:
+    explicit BluetoothSupplement(WebBluetooth*);
+
+    WebBluetooth* m_bluetooth;
+};
+
+} // namespace blink
+
+#endif // BluetoothRoutingId_h