MD Settings: Fix scrolling bugs and hacks caused by undefined load behavior

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

Index: chrome/browser/resources/settings/settings_page/main_page_behavior.js
diff --git a/chrome/browser/resources/settings/settings_page/main_page_behavior.js b/chrome/browser/resources/settings/settings_page/main_page_behavior.js
index ad4e84687e280c6d6ff6e910efb27491ee1d34a2..a8723ce554b254874658f76f5688c540012b9699 100644
--- a/chrome/browser/resources/settings/settings_page/main_page_behavior.js
+++ b/chrome/browser/resources/settings/settings_page/main_page_behavior.js
@@ -3,23 +3,6 @@
 // found in the LICENSE file.
 
 /**
- * Calls |readyTest| repeatedly until it returns true, then calls
- * |readyCallback|.
- * @param {function():boolean} readyTest
- * @param {!Function} readyCallback
- */
-function doWhenReady(readyTest, readyCallback) {
-  // TODO(dschuyler): Determine whether this hack can be removed.
-  // See also: https://github.com/Polymer/polymer/issues/3629
-  var intervalId = setInterval(function() {
-    if (readyTest()) {
-      clearInterval(intervalId);
-      readyCallback();
-    }
-  }, 10);
-}
-
-/**
  * Responds to route changes by expanding, collapsing, or scrolling to sections
  * on the page. Expanded sections take up the full height of the container. At
  * most one section should be expanded at any given time.
@@ -42,20 +25,11 @@ var MainPageBehaviorImpl = {
    * @param {settings.Route} oldRoute
    */
   currentRouteChanged: function(newRoute, oldRoute) {
-    if (oldRoute || !newRoute.section) {
+    // Allow the page to load before expanding the section.
+    if (!oldRoute)
+      setTimeout(this.tryTransitionToSection_.bind(this));
+    else
       this.tryTransitionToSection_();
-      return;
-    }
-
-    // Wait for the page to really be ready before expanding or scrolling to the
-    // section. TODO(michaelpg): Remove this workaround with a global workaround
-    // for crbug.com/638074.
-    doWhenReady(function() {
-      if (newRoute != settings.getCurrentRoute())
-        return;
-      var section = this.getSection(newRoute.section);
-      return section && (!newRoute.isSubpage() || section.canAnimateExpand());
-    }.bind(this), this.tryTransitionToSection_.bind(this));
   },
 
   /**
@@ -91,6 +65,10 @@ var MainPageBehaviorImpl = {
       }
     } else if (currentSection) {
       // Expand the section into a subpage or scroll to it on the main page.
+      if (!currentSection.clientHeight) {
+        setTimeout(this.tryTransitionToSection_.bind(this));
+        return;
+      }
       if (currentRoute.isSubpage())
         promise = this.expandSection_(currentSection);
       else
@@ -212,15 +190,15 @@ var MainPageBehaviorImpl = {
     return new Promise(function(resolve, reject) {
       // Wait for the other sections to show up so we can scroll properly.
       setTimeout(function() {
-        var newSection = settings.getCurrentRoute().section &&
-            this.getSection(settings.getCurrentRoute().section);
+        var currentRoute = settings.getCurrentRoute();
+        var newSection =
+            currentRoute.section && this.getSection(currentRoute.section);
 
-        // Scroll to the section if indicated by the route. TODO(michaelpg): Is
-        // this the right behavior, or should we return to the previous scroll
-        // position?
+        // Scroll to the new section if it's on this page. If the route has no
+        // section (e.g., a root page), return to the original position.
         if (newSection)
           newSection.scrollIntoView();
-        else
+        else if (!currentRoute.section)
           this.scroller.scrollTop = this.origScrollTop_;
 
         this.currentAnimation_ = section.animateCollapse(
@@ -243,17 +221,10 @@ var MainPageBehaviorImpl = {
 
   /** @private */
   scrollToSection_: function() {
-    doWhenReady(
-        function() {
-          return this.scrollHeight > 0;
-        }.bind(this),
-        function() {
-          // If the current section changes while we are waiting for the page to
-          // be ready, scroll to the newest requested section.
-          var section = this.getSection(settings.getCurrentRoute().section);
-          if (section)
-            section.scrollIntoView();
-        }.bind(this));
+    assert(this.scrollHeight > 0);
+    var section = this.getSection(settings.getCurrentRoute().section);
+    assert(section);
+    section.scrollIntoView();
   },
 
   /**