Speculative fix for single item page

After powerwash and sign in, the internal app item and page break item's
positions may be out of sync because model updater is not set. Then the
user has to wait til next sign in to get the most up to date position.
During the first sign in, the user may reorder or install new apps which
triggers single item page after next sign in.

Changes:
Set model updater for internal app and page break item.

Bug: 873853
Change-Id: I492234ceaf107deffdba056856a4f0a3c5df59e0
Reviewed-on: https://chromium-review.googlesource.com/c/1355178Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612500}

chrome/browser/ui/app_list/internal_app/internal_app_item.cc

@@ -41,6 +41,9 @@ InternalAppItem::InternalAppItem(
     UpdateFromSync(sync_item);
   else
     SetDefaultPositionIfApplicable(model_updater);
+
+  // Set model updater last to avoid being called during construction.
+  set_model_updater(model_updater);
 }
 
 InternalAppItem::~InternalAppItem() = default;

chrome/browser/ui/app_list/page_break_app_item.cc

@@ -24,6 +24,9 @@ PageBreakAppItem::PageBreakAppItem(
   }
 
   SetDefaultPositionIfApplicable(model_updater);
+
+  // Set model updater last to avoid being called during construction.
+  set_model_updater(model_updater);
 }
 
 PageBreakAppItem::~PageBreakAppItem() = default;