Bug 1720688 - Support extended attribute syntax in protocol declarations, r=mccr8

accessible/ipc/extension/mac/PDocAccessiblePlatformExt.ipdl

accessible/ipc/other/PDocAccessible.ipdl

dom/cache/PCacheStreamControl.ipdl

dom/canvas/PWebGL.ipdl

dom/file/ipc/PRemoteLazyInputStream.ipdl

dom/filesystem/PFileSystemRequest.ipdl

dom/gamepad/ipc/PGamepadEventChannel.ipdl

dom/gamepad/ipc/PGamepadTestChannel.ipdl

dom/indexedDB/PBackgroundIDBCursor.ipdl

dom/indexedDB/PBackgroundIDBFactory.ipdl

dom/indexedDB/PBackgroundIDBTransaction.ipdl

dom/indexedDB/PBackgroundIDBVersionChangeTransaction.ipdl

dom/ipc/PBrowser.ipdl

dom/ipc/PBrowserBridge.ipdl

dom/ipc/PContent.ipdl

dom/ipc/PInProcess.ipdl

dom/ipc/PWindowGlobal.ipdl

dom/media/gmp/PChromiumCDM.ipdl

dom/media/gmp/PGMPContent.ipdl

dom/media/gmp/PGMPService.ipdl