Handle the Encoding being a dictionary in PartialEvaluator_preEvaluateFont (bug 1157493)

*This is a regression from PR 4423.*

Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1157493.

src/core/evaluator.js

@@ -1567,6 +1567,21 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           hash.update(encoding.name);
         } else if (isRef(encoding)) {
           hash.update(encoding.num + '_' + encoding.gen);
+        } else if (isDict(encoding)) {
+          var keys = encoding.getKeys();
+          for (var i = 0, ii = keys.length; i < ii; i++) {
+            var entry = encoding.getRaw(keys[i]);
+            if (isName(entry)) {
+              hash.update(entry.name);
+            } else if (isRef(entry)) {
+              hash.update(entry.num + '_' + entry.gen);
+            } else if (isArray(entry)) { // 'Differences' entry.
+              // Ideally we should check the contents of the array, but to avoid
+              // parsing it here and then again in |extractDataStructures|,
+              // we only use the array length for now (fixes bug1157493.pdf).
+              hash.update(entry.length.toString());
+            }
+          }
         }
 
         var toUnicode = dict.get('ToUnicode') || baseDict.get('ToUnicode');

src/core/obj.js

@@ -192,6 +192,10 @@ var Dict = (function DictClosure() {
       return all;
     },
 
+    getKeys: function Dict_getKeys() {
+      return Object.keys(this.map);
+    },
+
     set: function Dict_set(key, value) {
       this.map[key] = value;
     },