Don't start the animation loop until the mouse starts dragging

Previously, the animation loop would run multiple times prior to the
the mouseup event on click. We only want to select to the current mouse
position if the mouse is actually dragged.

src/editor-component.coffee

@@ -284,16 +284,28 @@ EditorCompont = React.createClass
     @selectToMousePositionUntilMouseUp(event)
 
   selectToMousePositionUntilMouseUp: (event) ->
-    dragging = true
-    lastMousePosition = {clientX: event.clientX, clientY: event.clientY}
+    {editor} = @props
+    dragging = false
+    lastMousePosition = {}
+
+    animationLoop = =>
+      requestAnimationFrame =>
+        if dragging
+          @selectToMousePosition(lastMousePosition)
+          animationLoop()
 
     onMouseMove = (event) ->
-      # Stop dragging when cursor enters dev tools because we can't detect mouseup
-      dragging = false if event.which is 0
-
       lastMousePosition.clientX = event.clientX
       lastMousePosition.clientY = event.clientY
 
+      # Start the animation loop when the mouse moves prior to a mouseup event
+      unless dragging
+        dragging = true
+        animationLoop()
+
+      # Stop dragging when cursor enters dev tools because we can't detect mouseup
+      onMouseUp() if event.which is 0
+
     onMouseUp = ->
       dragging = false
       window.removeEventListener('mousemove', onMouseMove)
@@ -302,14 +314,6 @@ EditorCompont = React.createClass
     window.addEventListener('mousemove', onMouseMove)
     window.addEventListener('mouseup', onMouseUp)
 
-    animationLoop = =>
-      requestAnimationFrame =>
-        if dragging
-          @selectToMousePosition(lastMousePosition)
-          animationLoop()
-
-    animationLoop()
-
   selectToMousePosition: (event) ->
     @props.editor.selectToScreenPosition(@screenPositionForMouseEvent(event))