[ios] Update Fullscreen view when toolbarheight changes

FullscreenWebViewResizer's |-updateForCurrentState| is only called
in response to webview's frame KVO, but it also needs to be called when
the toolbar heights are changed since it changes the visible viewport.

Fixed: 1039658
Change-Id: Ib1afae58facfa85c358df0fc20f1aac7a2337acb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2052247
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741689}

ios/chrome/browser/ui/fullscreen/fullscreen_mediator.mm

@@ -95,6 +95,9 @@ void FullscreenMediator::FullscreenModelToolbarHeightsUpdated(
                                                  model_->min_toolbar_insets(),
                                                  model_->max_toolbar_insets());
   }
+  // Changes in the toolbar heights modifies the visible viewport so the WebView
+  // needs to be resized as needed.
+  [resizer_ updateForCurrentState];
 }
 
 void FullscreenMediator::FullscreenModelProgressUpdated(