Upstream Chrome on iOS source code [6/11].

ios/chrome/browser/ui/presenters/menu_presentation_controller.mm

+// Copyright 2016 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.
+
+// ======                        New Architecture                         =====
+// =         This code is only used in the new iOS Chrome architecture.       =
+// ============================================================================
+
+#import "ios/chrome/browser/ui/presenters/menu_presentation_controller.h"
+
+#import <QuartzCore/QuartzCore.h>
+
+#include "ios/chrome/browser/ui/presenters/menu_presentation_delegate.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@interface MenuPresentationController ()
+@property(nonatomic, weak) id<MenuPresentationDelegate> presentationDelegate;
+@property(nonatomic, assign) CGRect presentationFrame;
+@end
+
+@implementation MenuPresentationController
+@synthesize presentationDelegate = _presentationDelegate;
+@synthesize presentationFrame = _presentationFrame;
+
+#pragma mark - UIPresentationDelegate
+
+- (CGRect)frameOfPresentedViewInContainerView {
+  if (CGRectIsEmpty(self.presentationFrame)) {
+    [self updatePresentationDelegate];
+    if (self.presentationDelegate) {
+      self.presentationFrame =
+          [self.presentationDelegate frameForMenuPresentation:self];
+    } else {
+      // Placeholder default frame: something rectangular, 50 points in and
+      // down.
+      self.presentationFrame = CGRectMake(50, 50, 250, 300);
+    }
+  }
+  return self.presentationFrame;
+}
+
+- (void)presentationTransitionWillBegin {
+  self.presentedView.layer.borderWidth = 1.0;
+  self.presentedView.layer.shadowRadius = 1.0;
+  self.presentedView.layer.borderColor = [UIColor blackColor].CGColor;
+}
+
+#pragma mark - Private methods.
+
+// Checks if the presenting view controller conforms to
+// MenuPresentationDelegate and, if so, sets that view controller as the
+// presentation delegate. This can't be done at init time, becuase the
+// presenting view controller may not have been determined by UIKit yet.
+- (void)updatePresentationDelegate {
+  if ([self.presentingViewController
+          conformsToProtocol:@protocol(MenuPresentationDelegate)]) {
+    self.presentationDelegate = static_cast<id<MenuPresentationDelegate>>(
+        self.presentingViewController);
+  }
+}
+
+@end