Adding error handling to the connection flow.

remoting/ios/app/session_reconnect_view.mm

+// Copyright 2017 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.
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+#import "remoting/ios/app/session_reconnect_view.h"
+
+#import "ios/third_party/material_components_ios/src/components/Buttons/src/MaterialButtons.h"
+#import "remoting/ios/app/remoting_theme.h"
+
+static const CGFloat kReconnectButtonWidth = 120.f;
+static const CGFloat kReconnectButtonHeight = 30.f;
+
+@interface SessionReconnectView () {
+  MDCRaisedButton* _reconnectButton;
+}
+@end
+
+@implementation SessionReconnectView
+
+@synthesize delegate = _delegate;
+
+- (id)initWithFrame:(CGRect)frame {
+  self = [super initWithFrame:frame];
+  if (self) {
+    self.backgroundColor = [UIColor clearColor];
+
+    _reconnectButton = [[MDCRaisedButton alloc] init];
+    [_reconnectButton setElevation:4.0f forState:UIControlStateNormal];
+    [_reconnectButton setTitle:@"Reconnect" forState:UIControlStateNormal];
+    [_reconnectButton addTarget:self
+                         action:@selector(didTapReconnect:)
+               forControlEvents:UIControlEventTouchUpInside];
+    _reconnectButton.translatesAutoresizingMaskIntoConstraints = NO;
+    [self addSubview:_reconnectButton];
+
+    [self initializeLayoutConstraintsWithViews:NSDictionaryOfVariableBindings(
+                                                   _reconnectButton)];
+  }
+  return self;
+}
+
+- (void)initializeLayoutConstraintsWithViews:(NSDictionary*)views {
+  // Metrics to use in visual format strings.
+  NSDictionary* layoutMetrics = @{
+    @"reconnectButtonWidth" : @(kReconnectButtonWidth),
+    @"reconnectButtonHeight" : @(kReconnectButtonHeight),
+  };
+
+  [_reconnectButton.centerYAnchor constraintEqualToAnchor:self.centerYAnchor]
+      .active = YES;
+  [_reconnectButton.centerXAnchor constraintEqualToAnchor:self.centerXAnchor]
+      .active = YES;
+
+  [self addConstraints:[NSLayoutConstraint

[Yuwei, 2017/07/06 21:52:39]

For simple constraints like this I would probably do
[_reconnectButton.widthAnchor constraintEqualToConstant:kButtonWidth]

[nicholss, 2017/07/06 22:15:06]

Done.

[Yuwei, 2017/07/06 22:36:28]

FYI you could simplify these with array literal if you like

+                           constraintsWithVisualFormat:
+                               @"H:[_reconnectButton(reconnectButtonWidth)]"
+                                               options:0
+                                               metrics:layoutMetrics
+                                                 views:views]];
+
+  [self addConstraints:[NSLayoutConstraint
+                           constraintsWithVisualFormat:
+                               @"V:[_reconnectButton(reconnectButtonHeight)]"
+                                               options:0
+                                               metrics:layoutMetrics
+                                                 views:views]];
+  [self setNeedsUpdateConstraints];
+}
+
+#pragma mark - Private
+
+- (void)didTapReconnect:(id)sender {
+  if ([_delegate respondsToSelector:@selector(didTapReconnect)]) {
+    [_delegate didTapReconnect];
+  }
+}
+
+@end