WebUI: FindShortcutBehavior, default to listen on attach

Bug: 862839
Change-Id: Ie85e1abe1958665fef83f25c1eb3d437a2555f7b
Reviewed-on: https://chromium-review.googlesource.com/c/1396168Reviewed-by: Dan Beam <dbeam@chromium.org>
Commit-Queue: Esmael El-Moslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620116}

chrome/browser/resources/settings/languages_page/add_languages_dialog.js

@@ -48,12 +48,6 @@ Polymer({
   /** @override */
   attached: function() {
     this.$.dialog.showModal();
-    this.becomeActiveFindShortcutListener();
-  },
-
-  /** @override */
-  detached: function() {
-    this.removeSelfAsFindShortcutListener();
   },
 
   // Override FindShortcutBehavior methods.

chrome/browser/resources/settings/settings_page/settings_subpage.js

@@ -59,6 +59,9 @@ Polymer({
   /** @private {boolean} */
   lastActiveValue_: false,
 
+  // Override FindShortcutBehavior property.
+  findShortcutListenOnAttach: false,
+
   /** @override */
   attached: function() {
     if (!!this.searchLabel) {

chrome/browser/resources/settings/settings_ui/settings_ui.js

@@ -181,13 +181,10 @@ Polymer({
       scrollToTop(e.detail.bottom - this.$.container.clientHeight)
           .then(e.detail.callback);
     });
-
-    this.becomeActiveFindShortcutListener();
   },
 
   /** @override */
   detached: function() {
-    this.removeSelfAsFindShortcutListener();
     settings.resetRouteForTesting();
   },
 

ui/webui/resources/js/find_shortcut_behavior.js

@@ -62,6 +62,24 @@ const FindShortcutManager = (() => {
  * @polymerBehavior
  */
 const FindShortcutBehavior = {
+  /**
+   * @type {boolean}
+   * @protected
+   */
+  findShortcutListenOnAttach: true,
+
+  attached() {
+    if (this.findShortcutListenOnAttach) {
+      this.becomeActiveFindShortcutListener();
+    }
+  },
+
+  detached() {
+    if (this.findShortcutListenOnAttach) {
+      this.removeSelfAsFindShortcutListener();
+    }
+  },
+
   /**
    * If handled, return true.
    * @param {boolean} modalContextOpen