Web MIDI: introduce WebMIDIClient API to request a permission

public/platform/WebMIDIAccessorClient.h

Index: public/platform/WebMIDIAccessorClient.h
diff --git a/public/platform/WebMIDIAccessorClient.h b/public/platform/WebMIDIAccessorClient.h
index a4a590d474f5542b74329067bd5fe53ba58ca2b1..fba29d8970de1f9e7cf7b7d6b0f9b9c26ff93db2 100644
--- a/public/platform/WebMIDIAccessorClient.h
+++ b/public/platform/WebMIDIAccessorClient.h
@@ -41,6 +41,9 @@ public:
     virtual void didAddOutputPort(const WebString& id, const WebString& manufacturer, const WebString& name, const WebString& version) = 0;
 
     virtual void didAllowAccess() = 0;

[Chris Rogers, 2013/07/10 23:05:48]

Now that permissions is being handled in another place, didAllowAccess() should
probably be re-named to something like "didAddPorts()" or "didStartSession()" or
something which doesn't have the word "allow" in it.

Seems ok to add this as a TODO for now.

[Takashi Toyoshima, 2013/07/10 23:52:38]

Renamed to didStartSession.

+
+    // FIXME: Remove this obsoleted API. Now access permission is handled though the WebMIDIClient API.
+    // Only didAllowAccess() is used to notice the completion of adding all ports.
     virtual void didBlockAccess() = 0;
 
     // |timeStamp| is in milliseconds according to the Web MIDI API.