Pause measurement on overflowchanged during updates

Content updates trigger overflowchanged, but we're mainly using it to
detect when the editor component has been resized. Pausing measurement
during content updates makes them faster.

src/editor-scroll-view-component.coffee

@@ -1,5 +1,6 @@
 React = require 'react'
 {div} = require 'reactionary'
+{debounce} = require 'underscore-plus'
 
 InputComponent = require './input-component'
 LinesComponent = require './lines-component'
@@ -10,6 +11,10 @@ module.exports =
 EditorScrollViewComponent = React.createClass
   displayName: 'EditorScrollViewComponent'
 
+  measurementPaused: false
+  measurementPending: false
+  measurementRequested: false
+
   render: ->
     {editor, fontSize, fontFamily, lineHeight, showIndentGuide, cursorBlinkPeriod, cursorBlinkResumeDelay} = @props
     {visibleRowRange, preservedScreenRow, pendingChanges, cursorsMoved, onInputFocused, onInputBlurred} = @props
@@ -38,9 +43,34 @@ EditorScrollViewComponent = React.createClass
           SelectionsComponent({editor})
 
   componentDidMount: ->
-    @getDOMNode().addEventListener 'overflowchanged', @measureHeightAndWidth
+    @getDOMNode().addEventListener 'overflowchanged', @requestMeasurement
     @measureHeightAndWidth()
 
+  componentDidUpdate: ->
+    @pauseMeasurement()
+
+  requestMeasurement: ->
+    if @measurementPaused
+      @measurementRequested = true
+    else unless @measurementPending
+      @measurementPending = true
+      requestAnimationFrame =>
+        @measurementPending = false
+        @measureHeightAndWidth()
+
+  pauseMeasurement: ->
+    @measurementPaused = true
+    @resumeOverflowChangedEventsAfterDelay ?= debounce(@resumeMeasurement, 500)
+    @resumeOverflowChangedEventsAfterDelay()
+
+  resumeMeasurement: ->
+    @measurementPaused = false
+    if @measurementRequested
+      @measurementRequested = false
+      @requestMeasurement()
+
+  resumeMeasurementAfterDelay: null
+
   onInput: (char, replaceLastCharacter) ->
     {editor} = @props