replace per-page pdf highlight $watch with highlight event

services/web/public/coffee/ide/pdfng/directives/pdfPage.coffee

@@ -99,7 +99,7 @@ define [
 					highlights: highlightsElement
 				})
 
-				scope.$watch 'highlights', (highlights, oldVal) ->
+				scope.$on 'pdf:highlights', (event, highlights) ->
 					return unless highlights?
 					return unless highlights.length > 0
 					if scope.timeoutHandler

services/web/public/coffee/ide/pdfng/directives/pdfViewer.coffee

@@ -452,6 +452,8 @@ define [
 
 					return if !highlights.length
 
+					scope.$broadcast 'pdf:highlights', areas
+
 					first = highlights[0]
 
 					pageNum = scope.pages[first.page].pageNum