[iOS] Update view on DynamicType changes

This CL marks the WebState's view as dirty when the preferred content
size is changed. It causes the view to be laid out again.
It also changes the way the Overscroll controller is getting its
initialHeaderInset, by asking it to the delegate every time instead of
caching it, as the value become stale after changing the preferred
content size.

Bug: 892145
Change-Id: I2fe0b54a107e0cfed438ea5c57efdbb65fe4c5a3
Reviewed-on: https://chromium-review.googlesource.com/c/1307443
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605645}

ios/chrome/browser/ui/overscroll_actions/overscroll_actions_controller.mm

@@ -264,7 +264,6 @@ NSString* const kOverscrollActionsDidEnd = @"OverscrollActionsDidStop";
 @implementation OverscrollActionsController
 
 @synthesize overscrollActionView = _overscrollActionView;
-@synthesize initialHeaderInset = _initialHeaderInset;
 @synthesize initialHeaderHeight = _initialHeaderHeight;
 @synthesize overscrollState = _overscrollState;
 @synthesize delegate = _delegate;
@@ -876,11 +875,7 @@ NSString* const kOverscrollActionsDidEnd = @"OverscrollActionsDidStop";
 }
 
 - (CGFloat)initialHeaderInset {
-  if (_initialHeaderInset == 0) {
-    _initialHeaderInset =
-        [[self delegate] overscrollActionsControllerHeaderInset:self];
-  }
-  return _initialHeaderInset;
+  return [self.delegate overscrollActionsControllerHeaderInset:self];
 }
 
 #pragma mark - Bounce dynamic

ios/web/web_state/ui/crw_web_controller_container_view.mm

@@ -111,6 +111,15 @@
 
 #pragma mark Layout
 
+- (void)traitCollectionDidChange:(UITraitCollection*)previousTraitCollection {
+  [super traitCollectionDidChange:previousTraitCollection];
+  if (previousTraitCollection.preferredContentSizeCategory !=
+      self.traitCollection.preferredContentSizeCategory) {
+    // In case the preferred content size changes, the layout is dirty.
+    [self setNeedsLayout];
+  }
+}
+
 - (void)layoutSubviews {
   [super layoutSubviews];