Convert text-editor-component-spec to Babel for async/await

It's much easier to reason about async/await than Jasmine's
built-in queuing system, and using them made it easier to
debug flaky async tests.

spec/async-spec-helpers.coffee

@@ -0,0 +1,28 @@
+exports.beforeEach = (fn) ->
+  global.beforeEach ->
+    result = fn()
+    if result instanceof Promise
+      waitsForPromise(-> result)
+
+exports.afterEach = (fn) ->
+  global.afterEach ->
+    result = fn()
+    if result instanceof Promise
+      waitsForPromise(-> result)
+
+['it', 'fit', 'ffit', 'fffit'].forEach (name) ->
+  exports[name] = (description, fn) ->
+    global[name] description, ->
+      result = fn()
+      if result instanceof Promise
+        waitsForPromise(-> result)
+
+waitsForPromise = (fn) ->
+  promise = fn()
+  waitsFor 10000, (done) ->
+    promise.then(
+      done,
+      (error) ->
+        jasmine.getEnv().currentSpec.fail(error)
+        done()
+    )

src/display-buffer.coffee

@@ -1076,7 +1076,7 @@ class DisplayBuffer extends Model
 
     unless @didUpdateDecorationsEventScheduled
       @didUpdateDecorationsEventScheduled = true
-      process.nextTick =>
+      global.setImmediate =>
         @didUpdateDecorationsEventScheduled = false
         @emitter.emit 'did-update-decorations'
 

src/view-registry.coffee

@@ -224,8 +224,10 @@ class ViewRegistry
     # process updates requested as a result of reads
     writer() while writer = @documentWriters.shift()
 
+    resolveNextUpdatePromise = @resolveNextUpdatePromise
     @nextUpdatePromise = null
-    @resolveNextUpdatePromise?()
+    @resolveNextUpdatePromise = null
+    resolveNextUpdatePromise?()
 
   startPollingDocument: ->
     window.addEventListener('resize', @requestDocumentPoll)