[iOS] Fix NTP edge insets computation

The computation for the edge insets used by the NTP to resize itself
was using the fullscreen model which is updated too late to be used
here.
Instead, use directly the correct values.

Fixed: 1044329
Change-Id: Ibfe84cbe9abecd516f222e0e1d12a3fe6f1f7ca1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2019244Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735377}

ios/chrome/browser/ui/browser_view/browser_view_controller.mm

@@ -2498,12 +2498,12 @@ NSString* const kBrowserViewControllerSnackbarCategory =
 - (CGRect)ntpFrameForWebState:(web::WebState*)webState {
   NewTabPageTabHelper* NTPHelper = NewTabPageTabHelper::FromWebState(webState);
   DCHECK(NTPHelper && NTPHelper->IsActive());
-  // NTP expects to be laid out behind the bottom toolbar.
-  UIEdgeInsets viewportInsets = [self viewportInsetsForView:self.contentArea];
-  if (IsRegularXRegularSizeClass())
-    viewportInsets.bottom = 0.0;
-  if (IsSplitToolbarMode(self))
-    viewportInsets.top = 0;
+  // NTP is laid out only in the visible part of the screen.
+  UIEdgeInsets viewportInsets = UIEdgeInsetsZero;
+  if (!IsRegularXRegularSizeClass())
+    viewportInsets.bottom = [self bottomToolbarHeight];
+  if (!IsSplitToolbarMode(self))
+    viewportInsets.top = [self expandedTopToolbarHeight];
   return UIEdgeInsetsInsetRect(self.contentArea.bounds, viewportInsets);
 }