Bug 1150371 - [Part1] - Remove 'Learn more about Drm...' from r-click context menu if it's a MediaElement for clearkey content. r=florian

MozReview-Commit-ID: 2OrP7bM40pS

--HG--
extra : transplant_source : %9FN%84%7E%02%E8%F5%8A%40M%5C9%93%86%B4%A8%A4%85%01%9E

browser/base/content/nsContextMenu.js

@@ -735,7 +735,7 @@ nsContextMenu.prototype = {
         if (this.isMediaURLReusable(mediaURL)) {
           this.mediaURL = mediaURL;
         }
-        if (this.target.isEncrypted) {
+        if (this._isProprietaryDRM()) {
           this.onDRMMedia = true;
         }
         // Firefox always creates a HTMLVideoElement when loading an ogg file
@@ -754,7 +754,7 @@ nsContextMenu.prototype = {
         if (this.isMediaURLReusable(mediaURL)) {
           this.mediaURL = mediaURL;
         }
-        if (this.target.isEncrypted) {
+        if (this._isProprietaryDRM()) {
           this.onDRMMedia = true;
         }
       }
@@ -968,6 +968,11 @@ nsContextMenu.prototype = {
     return aNode.spellcheck;
   },
 
+  _isProprietaryDRM: function() {
+    return this.target.isEncrypted && this.target.mediaKeys &&
+           this.target.mediaKeys.keySystem != "org.w3.clearkey";
+  },
+
   _openLinkInParameters : function (extra) {
     let params = { charset: gContextMenuContentData.charSet,
                    referrerURI: gContextMenuContentData.documentURIObject,