[MD settings] observe changes to default font size in Appearance

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

Index: chrome/browser/resources/settings/appearance_page/appearance_page.js
diff --git a/chrome/browser/resources/settings/appearance_page/appearance_page.js b/chrome/browser/resources/settings/appearance_page/appearance_page.js
index 9039741b3736e81b204bfe2cd4a79ab3e86168c7..de1520abc79a477db6ddfbcf9dfa33597ce5f4f6 100644
--- a/chrome/browser/resources/settings/appearance_page/appearance_page.js
+++ b/chrome/browser/resources/settings/appearance_page/appearance_page.js
@@ -2,6 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+
+/**
+ * This is the absolute difference maintained between standard and
+ * fixed-width font sizes. http://crbug.com/91922.
+ * @const @private {number}
+ */
+var SIZE_DIFFERENCE_FIXED_STANDARD_ = 3;
+
+
 /**
  * 'settings-appearance-page' is the settings page containing appearance
  * settings.
@@ -110,12 +119,13 @@ Polymer({
   themeUrl_: '',
 
   observers: [
+    'onDefaultFontSizeChanged_(prefs.webkit.webprefs.default_font_size.value)',

[michaelpg, 2017/04/17 20:06:28]

nit: consistency w/ other observers: defaultFontSizeChanged_

[dschuyler, 2017/04/17 21:26:11]

Done.

     'themeChanged_(prefs.extensions.theme.id.value, useSystemTheme_)',
 
-// <if expr="is_linux and not chromeos">
+    // <if expr="is_linux and not chromeos">

[dschuyler, 2017/04/15 01:27:57]

This indention (here and below) is done by 
git cl format --js

     // NOTE: this pref only exists on Linux.
     'useSystemThemePrefChanged_(prefs.extensions.theme.use_system.value)',
-// </if>
+    // </if>
   ],
 
   created: function() {
@@ -165,6 +175,21 @@ Polymer({
     this.fire('refresh-pref', 'homepage');
   },
 
+  /**
+   * @param {number} value The changed font size slider value.
+   * @private
+   */
+  onDefaultFontSizeChanged_: function(value) {
+    // This is unusual but there is a pref that is dependent upon another.

[michaelpg, 2017/04/17 20:06:28]

as a *minor* nit, could you try to condense this comment a bit?

[dschuyler, 2017/04/17 21:26:11]

Done.

+    // Whenever the |default_font_size| is changed, this will update the
+    // |default_fixed_font_size| as well. They can (and are) handled separately
+    // in extensions. In the built-in settings (here), they are tied together to
+    // simplify the UI.
+    this.set(
+        'prefs.webkit.webprefs.default_fixed_font_size.value',
+        value - SIZE_DIFFERENCE_FIXED_STANDARD_);
+  },
+
   /** @private */
   onThemesTap_: function() {
     window.open(this.themeUrl_ || loadTimeData.getString('themesGalleryUrl'));
@@ -250,12 +275,12 @@ Polymer({
     }
 
     var i18nId;
-// <if expr="is_linux and not chromeos">
+    // <if expr="is_linux and not chromeos">
     i18nId = useSystemTheme ? 'systemTheme' : 'classicTheme';
-// </if>
-// <if expr="not is_linux or chromeos">
+    // </if>
+    // <if expr="not is_linux or chromeos">
     i18nId = 'chooseFromWebStore';
-// </if>
+    // </if>
     this.themeSublabel_ = this.i18n(i18nId);
     this.themeUrl_ = '';
   },