Web MIDI: introduce WebMIDIClient API to request a permission

Source/modules/modules.gypi

 {
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
     # ways.
     'extra_blink_module_idl_files': [],
     'extra_blink_module_files': [],
 
@@ skipping 652 matching lines @@
       'webdatabase/SQLTransactionStateMachine.h',
       'webdatabase/SQLTransactionSync.cpp',
       'webdatabase/SQLTransactionSync.h',
       'webdatabase/SQLTransactionSyncCallback.h',
       'webdatabase/WorkerGlobalScopeWebDatabase.cpp',
       'webdatabase/WorkerGlobalScopeWebDatabase.h',
       'webmidi/MIDIAccess.cpp',
       'webmidi/MIDIAccess.h',
       'webmidi/MIDIAccessPromise.cpp',
       'webmidi/MIDIAccessPromise.h',
+      'webmidi/MIDIClient.h',
+      'webmidi/MIDIController.cpp',
+      'webmidi/MIDIController.h',
       'webmidi/MIDIConnectionEvent.h',
       'webmidi/MIDIErrorCallback.h',
       'webmidi/MIDIInput.cpp',
       'webmidi/MIDIInput.h',
       'webmidi/MIDIMessageEvent.h',
       'webmidi/MIDIOptions.h',
       'webmidi/MIDIOutput.cpp',
       'webmidi/MIDIOutput.h',
       'webmidi/MIDIPort.cpp',
       'webmidi/MIDIPort.h',
@@ skipping 33 matching lines @@
       'websockets/WorkerThreadableWebSocketChannel.h',
     ],
     'modules_unittest_files': [
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketExtensionParserTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }