The old SDK event emitter API allowed to listen to all events on a given target via the special "*" type. The call sites can be found with the two following queries: - http://searchfox.org/mozilla-central/search?q=on(%22*%22&case=false&regexp=false&path=devtools - http://searchfox.org/mozilla-central/search?q=on%5C(%5B%5E%2C%5D%2B%2C%5Cs*%22%5C*%22&case=false&regexp=true&path=devtools Currently the feature is used in the following files: - devtools/client/framework/toolbox.js - devtools/client/performance/performance-controller.js - devtools/client/webaudioeditor/models.js - devtools/client/webaudioeditor/views/context.js - devtools/server/actors/performance.js - devtools/server/actors/profiler.js - devtools/server/actors/timeline.js - devtools/server/performance/recorder.js - devtools/shared/fronts/profiler.js We are adding additional backward compatibility code to devtools/shared/event-emitter.js in order to support the feature while we are migrating out of using SDK APIs in devtools. Ultimately we should try to get rid of this feature. and remove the dedicated implementation in event-emitter.js

Forgot to add this non-blocking follow up to the no-sdk triage.

Pushed by nchevobbe@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/2d398eeb8841 [devtools] Remove support for wildcard in EventEmitter. r=jdescottes.