Support current versions of PDF.js (#134)

In current versions of PDF.js, the `RenderingStates` enum is no longer
exported as a global, and the export method appears to be dependent on
the build configuration.

Since `RenderingStates` is a trivial enum, this commit fixes the problem
by just reproducing it in `pdfjs-rendering-states.js`.

h/static/scripts/annotator/anchoring/pdf.coffee

@@ -4,9 +4,9 @@ Annotator = require('annotator')
 xpathRange = Annotator.Range
 
 html = require('./html')
+RenderingStates = require('../pdfjs-rendering-states')
 {TextPositionAnchor, TextQuoteAnchor} = require('./types')
 
-
 # Caches for performance
 pageTextCache = {}
 quotePositionCache = {}

h/static/scripts/annotator/pdfjs-rendering-states.js

+'use strict';
+
+/**
+ * Enum values for page rendering states (IRenderableView#renderingState)
+ * in PDF.js. Taken from web/pdf_rendering_queue.js in the PDF.js library.
+ *
+ * Reproduced here because this enum is not exported consistently across
+ * different versions of PDF.js
+ */
+var RenderingStates = {
+  INITIAL: 0,
+  RUNNING: 1,
+  PAUSED: 2,
+  FINISHED: 3,
+};
+
+module.exports = RenderingStates;

h/static/scripts/annotator/plugin/pdf.coffee

 extend = require('extend')
 Annotator = require('annotator')
 
+RenderingStates = require('../pdfjs-rendering-states')
 
 module.exports = class PDF extends Annotator.Plugin
   documentLoaded: null