Fix bottom margin for NTP and FeedNTP on older Android versions

On pre-N versions, the layout parameters can be ignored if we don't
declare a root the inflated view. Updating the layout parameters only
after view is attached to window.

Bug: 895229
Change-Id: I671b83bbf6e72b9cbabb84e80636d68ba45c5dad
Reviewed-on: https://chromium-review.googlesource.com/c/1282105
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600137}

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

@@ -325,7 +325,16 @@ public class NewTabPage
         updateSearchProviderHasLogo();
 
         initializeMainView(activity);
+        getView().addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
+            @Override
+            public void onViewAttachedToWindow(View view) {
                 updateMargins(mTab.getBrowserControlsStateConstraints());
+                getView().removeOnAttachStateChangeListener(this);
+            }
+
+            @Override
+            public void onViewDetachedFromWindow(View view) {}
+        });
 
         eventReporter.onSurfaceOpened();
 
@@ -384,12 +393,7 @@ public class NewTabPage
         View view = getView();
         ViewGroup.MarginLayoutParams layoutParams =
                 ((ViewGroup.MarginLayoutParams) view.getLayoutParams());
-        if (layoutParams == null) {
-            // We could be updating the margin before the root view is attached to window.
-            layoutParams = new ViewGroup.MarginLayoutParams(
-                    ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
-            view.setLayoutParams(layoutParams);
-        }
+        if (layoutParams == null) return;
 
         int bottomMargin = 0;
         if (FeatureUtilities.isBottomToolbarEnabled()