Fix for margin not applied on navigating back

We need to update the bottom margin on initialization in case that
browser controls constraints are not updated during navigation.

Bug: 884803
Change-Id: I117aa9566b73cd1434d4f8b1331c08688b347573
Reviewed-on: https://chromium-review.googlesource.com/c/1277369Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598884}

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java

@@ -325,6 +325,7 @@ public class NewTabPage
         updateSearchProviderHasLogo();
 
         initializeMainView(activity);
+        updateMargins(mTab.getBrowserControlsStateConstraints());
 
         eventReporter.onSurfaceOpened();
 
@@ -377,7 +378,7 @@ public class NewTabPage
     }
 
     /** Update the margins for the content when browser controls constraints are changed. */
-    protected void updateMargins(@BrowserControlsState int constraints) {
+    private void updateMargins(@BrowserControlsState int constraints) {
         // TODO(mdjones): can this be merged with BasicNativePage's updateMargins?
 
         View view = getView();