[iOS] Adjust LongPress tips on iPad

On iPad, the LongPress tip should use the the kTabStripTabSwitcherGuide
instead of the kTabSwitcherGuide.

Bug: 875760
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I3dce36249a9b766e79473506770dd8fe565a0c28
Reviewed-on: https://chromium-review.googlesource.com/1180968Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584416}

ios/chrome/browser/ui/bubble/bubble_presenter.mm

@@ -187,7 +187,11 @@ const CGFloat kBubblePresentationDelay = 1;
   NSString* text = l10n_util::GetNSStringWithFixup(
       IDS_IOS_LONG_PRESS_TOOLBAR_IPH_PROMOTION_TEXT);
   CGPoint searchButtonAnchor =
-      [self anchorPointToGuide:kTabSwitcherGuide direction:arrowDirection];
+      IsRegularXRegularSizeClass()
+          ? [self anchorPointToGuide:kTabStripTabSwitcherGuide
+                           direction:arrowDirection]
+          : [self anchorPointToGuide:kTabSwitcherGuide
+                           direction:arrowDirection];
 
   // If the feature engagement tracker does not consider it valid to display
   // the tip, then end early to prevent the potential reassignment of the