[ios] Fixed web-compat bug related to resetting top content inset.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/overscroll_actions/overscroll_actions_controller.h"
 
 #import <QuartzCore/QuartzCore.h>
 
 #include <algorithm>
 #include "base/logging.h"
@@ skipping 178 matching lines @@
 // overscroll controller is in OverscrollStateActionReady.
 @property(nonatomic, assign) CGPoint panPointScreenOrigin;
 // Pan gesture recognizer used to track horizontal touches.
 @property(nonatomic, retain) UIPanGestureRecognizer* panGestureRecognizer;
 
 // Registers notifications to lock the overscroll actions on certain UI states.
 - (void)registerNotifications;
 // Setup/tearDown methods are used to register values when the delegate is set.
 - (void)tearDown;
 - (void)setup;
+// Resets scroll view's top content inset to |self.initialContentInset|.
+- (void)resetScrollViewTopContentInset;
 // Access the headerView from the delegate.
 - (UIView<RelaxedBoundsConstraintsHitTestSupport>*)headerView;
 // Locking/unlocking methods used to disable/enable the overscroll actions
 // with a reference count.
 - (void)incrementOverscrollActionLockForNotification:
     (NSNotification*)notification;
 - (void)decrementOverscrollActionLockForNotification:
     (NSNotification*)notification;
 // Indicates whether the overscroll action is allowed.
 - (BOOL)isOverscrollActionEnabled;
@@ skipping 165 matching lines @@
          (isScrolledToTop && isMinimumTimeBetweenScrollRespected &&
           delegateAllowOverscrollActions && !isZooming);
 }
 
 - (void)scrollViewDidEndDraggingWillDecelerate:(BOOL)decelerate
                                  contentOffset:(CGPoint)contentOffset {
   // Content is now hidden behind toolbar, make sure that contentInset is
   // restored to initial value.
   if (contentOffset.y >= 0 ||
       self.overscrollState == ios_internal::OverscrollState::NO_PULL_STARTED) {
-    [self setScrollViewContentInset:UIEdgeInsetsMake(self.initialContentInset,
-                                                     0, 0, 0)];
+    [self resetScrollViewTopContentInset];
   }
 
   [self triggerActionIfNeeded];
   _allowPullingActions = NO;
 }
 
 - (void)scrollViewWillEndDraggingWithVelocity:(CGPoint)velocity
                           targetContentOffset:
                               (inout CGPoint*)targetContentOffset {
   if (![self isOverscrollActionEnabled])
@@ skipping 187 matching lines @@
   }
 }
 
 - (void)setScrollViewContentInset:(UIEdgeInsets)contentInset {
   if (_scrollview)
     [_scrollview setContentInset:contentInset];
   else
     [_webViewScrollViewProxy setContentInset:contentInset];
 }
 
+- (void)resetScrollViewTopContentInset {
+  UIEdgeInsets contentInset = self.scrollView.contentInset;
+  contentInset.top = self.initialContentInset;
+  [self setScrollViewContentInset:contentInset];
+}
+
 - (UIView<RelaxedBoundsConstraintsHitTestSupport>*)headerView {
   return [self.delegate headerView];
 }
 
 - (void)incrementOverscrollActionLockForNotification:(NSNotification*)notif {
   if (![_lockIncrementNotifications containsObject:notif.name]) {
     [_lockIncrementNotifications addObject:notif.name];
     ++_overscrollActionLock;
   }
 }
@@ skipping 269 matching lines @@
   _panGestureRecognizer.enabled = YES;
   [self scrollView].panGestureRecognizer.enabled = NO;
   [self scrollView].panGestureRecognizer.enabled = YES;
   [self startBounceWithInitialVelocity:CGPointZero];
   [self.delegate
       overscrollActionsController:self
                  didTriggerAction:self.overscrollActionView.selectedAction];
 }
 
 @end