MD Settings: fix infinite setInterval loop

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 78bfe20f7512cb76e14f133ccba95ad8b8bd513a..7a53a64bac54c0e4129f34cdf29acddc88c260dc 100644
--- a/chrome/browser/resources/settings/settings_page/main_page_behavior.js
+++ b/chrome/browser/resources/settings/settings_page/main_page_behavior.js
@@ -31,6 +31,11 @@ function doWhenReady(readyTest, readyCallback) {
  * @polymerBehavior MainPageBehavior
  */
 var MainPageBehaviorImpl = {
+  properties: {
+    // Name of the root route corresponding to this page.
+    route: String,
+  },
+
   /** @type {?HTMLElement} The scrolling container. */
   scroller: null,
 
@@ -54,7 +59,14 @@ var MainPageBehaviorImpl = {
     } else {
       doWhenReady(
         function() {
-          return this.scrollHeight > 0;
+          if (this.scrollHeight > 0)
+            return true;
+
+          // Height is irrelevant if this page isn't the current page.

[Dan Beam, 2016/09/01 03:05:15]

nit:  // This is not the page you're looking for.

</kenobi>

[dschuyler, 2016/09/01 18:28:42]

nit: I suggest dropping the comment (rather 
than changing it - though the change is funny).

+          if (!settings.Route[this.route].contains(settings.getCurrentRoute()))

[tommycli, 2016/09/01 18:14:24]

holy shit that's clever.

[michaelpg, 2016/09/01 19:34:46]

I was hoping to just do:

    if (this.domHost.getPage(settings.getCurrentRoute()) != this)

but then we'd have a cyclic dependency between settings_main and
main_page_behavior. There are also other problems, thanks to closure not
understanding the concept of behaviors, that would make it cumbersome.

Anyway, everything will continue being overly complicated until we move most of
MainPageBehavior's responsibilities to settings-main. It's crazy we let two
elements (advanced and basic) control the same scroller.

+            return true;
+
+          return false;

[dschuyler, 2016/09/01 20:38:02]

Please combine these into:

return this.scrollHeight > 0 ||
    !settings.Route[this.route].contains(settings.getCurrentRoute());

         }.bind(this),
         this.tryTransitionToSection_.bind(this));
     }