[ios] Fix Fake Omnibox bug when sticking to top of NTP

The logic in NTPViewController's -offsetToStickOmnibox to determine
when to stick the fake omnibox to the top of the surface is not the
same as the one within the NewTabPageView that determines when the
fake omnibox expansion animation stops (which happens to be the same
position as where it should stick to the top of surface). This change
makes NewTabPageView's logic public to the NTPViewController.

Video: https://drive.google.com/file/d/1tmjMxIrzQjah1wlUzXfrerpYV-M8TKV2/view?usp=sharing

(cherry picked from commit 6053917)

Fixed: 1443603
Change-Id: I0aa81e8aceb77cae41068b08db70be08e2d2bda2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4569060
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Scott Yoder <scottyoder@google.com>
Cr-Original-Commit-Position: refs/heads/main@{#1150978}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4581659
Auto-Submit: Chris Lu <thegreenfrog@chromium.org>
Commit-Queue: Scott Yoder <scottyoder@google.com>
Cr-Commit-Position: refs/branch-heads/5790@{#265}
Cr-Branched-From: 1d71a33-refs/heads/main@{#1148114}

ios/chrome/browser/ui/ntp/new_tab_page_header_view.h

@@ -52,6 +52,9 @@
 - (CGFloat)searchFieldProgressForOffset:(CGFloat)offset
                          safeAreaInsets:(UIEdgeInsets)safeAreaInsets;
 
+// The positive offset value to begin the fake omniobx expansion animation.
+- (CGFloat)offsetToBeginFakeOmniboxExpansionForSplitMode;
+
 // Changes the constraints of searchField based on its initialFrame and the
 // scroll view's y `offset`. Also adjust the alpha values for `_searchBoxBorder`
 // and `_shadow` and the constant values for the `constraints`. `screenWidth` is

ios/chrome/browser/ui/ntp/new_tab_page_header_view.mm

@@ -363,18 +363,7 @@ - (void)addSeparatorToSearchField:(UIView*)searchField {
 - (CGFloat)searchFieldProgressForOffset:(CGFloat)offset
                          safeAreaInsets:(UIEdgeInsets)safeAreaInsets {
   // The scroll offset at which point searchField's frame should stop growing.
-  CGFloat maxScaleOffset = self.frame.size.height - ToolbarHeight() -
-                           ntp_header::kFakeOmniboxScrolledToTopMargin -
-                           safeAreaInsets.top;
-  // If the Shrunk logo for the Start Surface is being shown, the searchField
-  // expansion should start later so that its background does not cut off the
-  // logo. This mainly impacts notched devices that have a large top Safe Area
-  // inset. Instead of ensuring the expansion finishes by the time the omnibox
-  // reaches the bottom of the toolbar, wait until the logo is in the safe area
-  // before expanding so it is out of view.
-  if (ShouldShrinkLogoForStartSurface()) {
-    maxScaleOffset += safeAreaInsets.top;
-  }
+  CGFloat maxScaleOffset = [self offsetToBeginFakeOmniboxExpansionForSplitMode];
   // If it is not in SplitMode the search field should scroll under the toolbar.
   if (!IsSplitToolbarMode(self)) {
     maxScaleOffset += ToolbarHeight();
@@ -392,6 +381,11 @@ - (CGFloat)searchFieldProgressForOffset:(CGFloat)offset
   return percent;
 }
 
+- (CGFloat)offsetToBeginFakeOmniboxExpansionForSplitMode {
+  return self.frame.size.height - ToolbarHeight() -
+         ntp_header::kFakeOmniboxScrolledToTopMargin;
+}
+
 - (void)updateSearchFieldWidth:(NSLayoutConstraint*)widthConstraint
                         height:(NSLayoutConstraint*)heightConstraint
                      topMargin:(NSLayoutConstraint*)topMarginConstraint

ios/chrome/browser/ui/ntp/new_tab_page_header_view_controller.h

@@ -110,6 +110,9 @@
 // Update any dynamic constraints.
 - (void)updateConstraints;
 
+// The positive offset value to begin the fake omniobx expansion animation.
+- (CGFloat)offsetToBeginFakeOmniboxExpansionForSplitMode;
+
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_NTP_NEW_TAB_PAGE_HEADER_VIEW_CONTROLLER_H_

ios/chrome/browser/ui/ntp/new_tab_page_header_view_controller.mm

@@ -303,6 +303,10 @@ - (void)viewDidAppear:(BOOL)animated {
   }
 }
 
+- (CGFloat)offsetToBeginFakeOmniboxExpansionForSplitMode {
+  return [self.headerView offsetToBeginFakeOmniboxExpansionForSplitMode];
+}
+
 #pragma mark - Private
 
 // Initialize and add a search field tap target and a voice search button.

ios/chrome/browser/ui/ntp/new_tab_page_view_controller.mm

@@ -1480,17 +1480,12 @@ - (CGFloat)offsetWhenScrolledIntoFeed {
 // The y-position content offset for when the fake omnibox
 // should stick to the top of the NTP.
 - (CGFloat)offsetToStickOmnibox {
-  CGFloat offset =
-      -(self.headerViewController.view.frame.size.height -
-        [self stickyOmniboxHeight] -
-        [self.feedHeaderViewController customSearchEngineViewHeight]);
-  if (IsSplitToolbarMode(self)) {
-    offset -= [self contentSuggestionsContentHeight];
-  }
-  if (self.feedTopSectionViewController) {
-    offset -= self.feedTopSectionViewController.view.frame.size.height;
-  }
-  return offset;
+  // Do not need to factor in safeAreaInsets.top because the fake omnibox sticks
+  // below it, so it is effectively just the scroll distance between top of
+  // NTPHeader and the top of the Fake Omnibox.
+  return -([self heightAboveFeed] -
+           [self.headerViewController
+                   offsetToBeginFakeOmniboxExpansionForSplitMode]);
 }
 
 // Whether the collection view has attained its minimum height.