[iOS] Refactored NTP scroll when tapping omnibox

Refactored NTP offset starts negative because of the way the content
suggestions header are added on top of the feed. Fixes header
synchronizer by using additional offset property to compensate for the
negative offset.

Bug: 1114792
Change-Id: I62d2be34444d705e8ad7fd862ded80e9e947b783
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626830
Commit-Queue: Adam Trudeau-Arcaro <adamta@google.com>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843128}

ios/chrome/browser/ui/content_suggestions/content_suggestions_header_synchronizer.mm

@@ -122,8 +122,7 @@ initWithCollectionController:
   if (self.collectionView.decelerating) {
     // Stop the scrolling if the scroll view is decelerating to prevent the
     // focus to be immediately lost.
-    [self.collectionView setContentOffset:self.collectionView.contentOffset
-                                 animated:NO];
+    [self.collectionView setContentOffset:[self adjustedOffset] animated:NO];
   }
 
   if (self.collectionController.scrolledToTop) {
@@ -138,7 +137,7 @@ initWithCollectionController:
 
   CGFloat pinnedOffsetY = [self.headerController pinnedOffsetY];
   self.collectionShiftingOffset =
-      MAX(0, pinnedOffsetY - self.collectionView.contentOffset.y);
+      MAX(0, pinnedOffsetY - [self adjustedOffset].y);
 
   self.collectionController.scrolledToTop = YES;
   self.shouldAnimateHeader = YES;
@@ -153,13 +152,14 @@ initWithCollectionController:
                 return;
 
               __typeof(weakSelf) strongSelf = weakSelf;
-              if (strongSelf.collectionView.contentOffset.y < pinnedOffsetY) {
+              if ((strongSelf.collectionView.contentOffset.y +
+                   self.additionalOffset) < pinnedOffsetY) {
                 if (animations)
                   animations();
                 // Changing the contentOffset of the collection results in a
                 // scroll and a change in the constraints of the header.
                 strongSelf.collectionView.contentOffset =
-                    CGPointMake(0, pinnedOffsetY);
+                    CGPointMake(0, pinnedOffsetY - self.additionalOffset);
                 // Layout the header for the constraints to be animated.
                 [strongSelf.headerController layoutHeader];
                 [strongSelf.collectionView
@@ -211,10 +211,8 @@ initWithCollectionController:
 
   if (self.shouldAnimateHeader) {
     UIEdgeInsets insets = self.collectionView.safeAreaInsets;
-    CGFloat totalOffset =
-        self.collectionView.contentOffset.y + self.additionalOffset;
     [self.headerController
-        updateFakeOmniboxForOffset:totalOffset
+        updateFakeOmniboxForOffset:[self adjustedOffset].y
                        screenWidth:self.collectionView.frame.size.width
                     safeAreaInsets:insets];
   }
@@ -229,9 +227,7 @@ initWithCollectionController:
     // -viewDidLayoutSubviews.  Since self.collectionView and it's superview
     // should always have the same safeArea, this should be safe.
     UIEdgeInsets insets = self.collectionView.superview.safeAreaInsets;
-    CGFloat totalOffset =
-        self.collectionView.contentOffset.y + self.additionalOffset;
-    [self.headerController updateFakeOmniboxForOffset:totalOffset
+    [self.headerController updateFakeOmniboxForOffset:[self adjustedOffset].y
                                           screenWidth:width
                                        safeAreaInsets:insets];
   } else {
@@ -267,6 +263,32 @@ initWithCollectionController:
   return self.headerController.isShowing;
 }
 
+#pragma mark - UIGestureRecognizerDelegate
+
+- (BOOL)gestureRecognizer:(UIGestureRecognizer*)gestureRecognizer
+       shouldReceiveTouch:(UITouch*)touch {
+  BOOL isMostVisitedCell =
+      content_suggestions::nearestAncestor(
+          touch.view, [ContentSuggestionsMostVisitedCell class]) != nil;
+  BOOL isMostVisitedActionCell =
+      content_suggestions::nearestAncestor(
+          touch.view, [ContentSuggestionsMostVisitedActionCell class]) != nil;
+  BOOL isSuggestionCell =
+      content_suggestions::nearestAncestor(
+          touch.view, [ContentSuggestionsCell class]) != nil;
+  return !isMostVisitedCell && !isMostVisitedActionCell && !isSuggestionCell;
+}
+
+- (UIView*)nearestAncestorOfView:(UIView*)view withClass:(Class)aClass {
+  if (!view) {
+    return nil;
+  }
+  if ([view isKindOfClass:aClass]) {
+    return view;
+  }
+  return [self nearestAncestorOfView:[view superview] withClass:aClass];
+}
+
 #pragma mark - Private
 
 // Convenience method to get the collection view of the suggestions.
@@ -306,30 +328,11 @@ initWithCollectionController:
   }
 }
 
-#pragma mark - UIGestureRecognizerDelegate
-
-- (BOOL)gestureRecognizer:(UIGestureRecognizer*)gestureRecognizer
-       shouldReceiveTouch:(UITouch*)touch {
-  BOOL isMostVisitedCell =
-      content_suggestions::nearestAncestor(
-          touch.view, [ContentSuggestionsMostVisitedCell class]) != nil;
-  BOOL isMostVisitedActionCell =
-      content_suggestions::nearestAncestor(
-          touch.view, [ContentSuggestionsMostVisitedActionCell class]) != nil;
-  BOOL isSuggestionCell =
-      content_suggestions::nearestAncestor(
-          touch.view, [ContentSuggestionsCell class]) != nil;
-  return !isMostVisitedCell && !isMostVisitedActionCell && !isSuggestionCell;
-}
-
-- (UIView*)nearestAncestorOfView:(UIView*)view withClass:(Class)aClass {
-  if (!view) {
-    return nil;
-  }
-  if ([view isKindOfClass:aClass]) {
-    return view;
-  }
-  return [self nearestAncestorOfView:[view superview] withClass:aClass];
+// Returns y-offset compensated for any additionalOffset that might be set.
+- (CGPoint)adjustedOffset {
+  CGPoint adjustedOffset = self.collectionView.contentOffset;
+  adjustedOffset.y += self.additionalOffset;
+  return adjustedOffset;
 }
 
 @end