visionOS: Date picker Close/Reset buttons have no padding from the ed…

…ge of the window

https://bugs.webkit.org/show_bug.cgi?id=274123
rdar://127908565

Reviewed by Aditya Keerthi.

* Source/WebKit/UIProcess/ios/forms/WKDatePickerPopoverController.mm:
(-[WKDatePickerPopoverView initWithDatePicker:]):
Add some padding to the accessory view, which contains the Close and Reset buttons.
Only do so when the app is using the visionOS idiom (curiously, the popover style
tracks the app, not the WKWebView's idiom).

Canonical link: https://commits.webkit.org/278727@main

Source/WebKit/UIProcess/ios/forms/WKDatePickerPopoverController.mm

@@ -30,6 +30,7 @@
 
 #import "UIKitUtilities.h"
 #import <WebCore/LocalizedStrings.h>
+#import <pal/system/ios/UserInterfaceIdiom.h>
 #import <wtf/BlockPtr.h>
 #import <wtf/RetainPtr.h>
 #import <wtf/text/WTFString.h>
@@ -86,6 +87,8 @@ - (instancetype)initWithDatePicker:(UIDatePicker *)datePicker
     _contentSize.width = 2 * marginSize + std::max<CGFloat>(datePickerSize.width, accessoryViewSize.width);
     _contentSize.height = toolbarBottomMargin + 2 * marginSize + datePickerSize.height + accessoryViewSize.height;
 
+    auto accessoryViewHorizontalMargin = PAL::currentUserInterfaceIdiomIsVision() ? marginSize : 0;
+
     [NSLayoutConstraint activateConstraints:@[
         [self.widthAnchor constraintEqualToConstant:_contentSize.width],
         [self.heightAnchor constraintEqualToConstant:_contentSize.height],
@@ -98,8 +101,8 @@ - (instancetype)initWithDatePicker:(UIDatePicker *)datePicker
         [[_datePicker trailingAnchor] constraintEqualToAnchor:self.trailingAnchor],
         [[_datePicker topAnchor] constraintEqualToAnchor:self.topAnchor],
         [[_datePicker bottomAnchor] constraintEqualToSystemSpacingBelowAnchor:[_accessoryView topAnchor] multiplier:1],
-        [[_accessoryView leadingAnchor] constraintEqualToAnchor:self.leadingAnchor],
-        [[_accessoryView trailingAnchor] constraintEqualToAnchor:self.trailingAnchor],
+        [[_accessoryView leadingAnchor] constraintEqualToAnchor:self.leadingAnchor constant:accessoryViewHorizontalMargin],
+        [[_accessoryView trailingAnchor] constraintEqualToAnchor:self.trailingAnchor constant:-accessoryViewHorizontalMargin],
         [[_accessoryView heightAnchor] constraintEqualToConstant:accessoryViewSize.height],
         [[_accessoryView bottomAnchor] constraintEqualToAnchor:[_backgroundView bottomAnchor]],
     ]];