Fix inconsistent spacing and trailing commas in objects in web/ files, so we can enable the comma-dangle and object-curly-spacing ESLint rules later on

http://eslint.org/docs/rules/comma-dangle
http://eslint.org/docs/rules/object-curly-spacing

Given that we currently have quite inconsistent object formatting, fixing this in in *one* big patch probably wouldn't be feasible (since I cannot imagine anyone wanting to review that); hence I've opted to try and do this piecewise instead.

*Please note:* This patch was created automatically, using the ESLint `--fix` command line option. In a couple of places this caused lines to become too long, and I've fixed those manually; please refer to the interdiff below for the only hand-edits in this patch.

```diff
diff --git a/web/pdf_thumbnail_view.js b/web/pdf_thumbnail_view.js
index 002dbf29..1de4e530 100644
--- a/web/pdf_thumbnail_view.js
+++ b/web/pdf_thumbnail_view.js
@@ -420,8 +420,8 @@ var PDFThumbnailView = (function PDFThumbnailViewClosure() {
     setPageLabel: function PDFThumbnailView_setPageLabel(label) {
       this.pageLabel = (typeof label === 'string' ? label : null);

-      this.l10n.get('thumb_page_title', { page: this.pageId, }, 'Page {{page}}').
-          then((msg) => {
+      this.l10n.get('thumb_page_title', { page: this.pageId, },
+                    'Page {{page}}').then((msg) => {
         this.anchor.title = msg;
       });

diff --git a/web/secondary_toolbar.js b/web/secondary_toolbar.js
index 160e0410..6495fc5e 100644
--- a/web/secondary_toolbar.js
+++ b/web/secondary_toolbar.js
@@ -65,7 +65,8 @@ class SecondaryToolbar {
       { element: options.printButton, eventName: 'print', close: true, },
       { element: options.downloadButton, eventName: 'download', close: true, },
       { element: options.viewBookmarkButton, eventName: null, close: true, },
-      { element: options.firstPageButton, eventName: 'firstpage', close: true, },
+      { element: options.firstPageButton, eventName: 'firstpage',
+        close: true, },
       { element: options.lastPageButton, eventName: 'lastpage', close: true, },
       { element: options.pageRotateCwButton, eventName: 'rotatecw',
         close: false, },
@@ -76,7 +77,7 @@ class SecondaryToolbar {
       { element: options.cursorHandToolButton, eventName: 'switchcursortool',
         eventDetails: { tool: CursorTool.HAND, }, close: true, },
       { element: options.documentPropertiesButton,
-        eventName: 'documentproperties', close: true, }
+        eventName: 'documentproperties', close: true, },
     ];
     this.items = {
       firstPage: options.firstPageButton,
```

web/firefoxcom.js

@@ -75,10 +75,10 @@ var FirefoxCom = (function FirefoxComClosure() {
         action,
         data,
         sync: false,
-        responseExpected: !!callback
+        responseExpected: !!callback,
       });
       return request.dispatchEvent(sender);
-    }
+    },
   };
 })();
 
@@ -101,7 +101,7 @@ var DownloadManager = (function DownloadManagerClosure() {
         blobUrl,
         originalUrl: blobUrl,
         filename,
-        isAttachment: true
+        isAttachment: true,
       });
     },
 
@@ -119,7 +119,7 @@ var DownloadManager = (function DownloadManagerClosure() {
         originalUrl: url,
         filename,
       }, onResponse);
-    }
+    },
   };
 
   return DownloadManager;
@@ -179,7 +179,7 @@ class MozL10n {
       phraseSearch: true,
       caseSensitive: !!evt.detail.caseSensitive,
       highlightAll: !!evt.detail.highlightAll,
-      findPrevious: !!evt.detail.findPrevious
+      findPrevious: !!evt.detail.findPrevious,
     });
   };
 
@@ -305,7 +305,7 @@ document.mozL10n.setExternalLocalizerServices({
 
   getStrings(key) {
     return FirefoxCom.requestSync('getStrings', key);
-  }
+  },
 });
 
 export {