MD Settings: Convert all browser proxies to use ES6 class syntax.

chrome/browser/resources/settings/appearance_page/fonts_browser_proxy.js

Index: chrome/browser/resources/settings/appearance_page/fonts_browser_proxy.js
diff --git a/chrome/browser/resources/settings/appearance_page/fonts_browser_proxy.js b/chrome/browser/resources/settings/appearance_page/fonts_browser_proxy.js
index b8b1263af399105c6e6552ec3edc0e9d4b0eee2a..d513b3ad19e37786d68790460b3a0bdaeb646bc5 100644
--- a/chrome/browser/resources/settings/appearance_page/fonts_browser_proxy.js
+++ b/chrome/browser/resources/settings/appearance_page/fonts_browser_proxy.js
@@ -12,44 +12,39 @@ var FontsData;
 
 cr.define('settings', function() {
   /** @interface */
-  function FontsBrowserProxy() {}
-
-  FontsBrowserProxy.prototype = {
+  class FontsBrowserProxy {
     /**
      * @return {!Promise<!FontsData>} Fonts and the advanced font settings
      *     extension URL.
      */
-    fetchFontsData: assertNotReached,
+    fetchFontsData() {}
 
-    observeAdvancedFontExtensionAvailable: assertNotReached,
+    observeAdvancedFontExtensionAvailable() {}
 
-    openAdvancedFontSettings: assertNotReached,

[scottchen, 2017/06/27 21:14:10]

for future readers:
Had a discussion with @dpapad about assertNotReached logic being removed, and
concluded that we didn't need it originally anyway, because the implementations
wasn't doing actual sub-classing, so the methods were not gonna fall through
anyway.

-  };
+    openAdvancedFontSettings() {}
+  }
 
   /**
    * @implements {settings.FontsBrowserProxy}
-   * @constructor
    */
-  function FontsBrowserProxyImpl() {}
-
-  cr.addSingletonGetter(FontsBrowserProxyImpl);
-
-  FontsBrowserProxyImpl.prototype = {
+  class FontsBrowserProxyImpl {
     /** @override */
-    fetchFontsData: function() {
+    fetchFontsData() {
       return cr.sendWithPromise('fetchFontsData');
-    },
+    }
 
     /** @override */
-    observeAdvancedFontExtensionAvailable: function() {
+    observeAdvancedFontExtensionAvailable() {
       chrome.send('observeAdvancedFontExtensionAvailable');
-    },
+    }
 
     /** @override */
-    openAdvancedFontSettings: function() {
+    openAdvancedFontSettings() {
       chrome.send('openAdvancedFontSettings');
     }
-  };
+  }
+
+  cr.addSingletonGetter(FontsBrowserProxyImpl);
 
   return {
     FontsBrowserProxy: FontsBrowserProxy,