Some minor doc typo and diagnostic fixes.

lib/ui/channel_buffers.dart

@@ -330,7 +330,8 @@ class ChannelBuffers {
         'framework has had an opportunity to register a listener. See the ChannelBuffers '
         'API documentation for details on how to configure the channel to expect more '
         'messages, or to expect messages to get discarded:\n'
-        '  https://api.flutter.dev/flutter/dart-ui/ChannelBuffers-class.html'
+        '  https://api.flutter.dev/flutter/dart-ui/ChannelBuffers-class.html\n'
+        'The capacity of the $name channel is ${channel._capacity} message${channel._capacity != 1 ? 's' : ''}.',
       );
     }
   }

lib/ui/window/platform_configuration.cc

@@ -379,17 +379,17 @@ void PlatformConfigurationNativeApi::SetIsolateDebugName(
   UIDartState::Current()->SetDebugName(name);
 }
 
-Dart_PerformanceMode PlatformConfigurationNativeApi::current_performace_mode_ =
+Dart_PerformanceMode PlatformConfigurationNativeApi::current_performance_mode_ =
     Dart_PerformanceMode_Default;
 
 Dart_PerformanceMode PlatformConfigurationNativeApi::GetDartPerformanceMode() {
-  return current_performace_mode_;
+  return current_performance_mode_;
 }
 
 int PlatformConfigurationNativeApi::RequestDartPerformanceMode(int mode) {
   UIDartState::ThrowIfUIOperationsProhibited();
-  current_performace_mode_ = static_cast<Dart_PerformanceMode>(mode);
-  return Dart_SetPerformanceMode(current_performace_mode_);
+  current_performance_mode_ = static_cast<Dart_PerformanceMode>(mode);
+  return Dart_SetPerformanceMode(current_performance_mode_);
 }
 
 Dart_Handle PlatformConfigurationNativeApi::GetPersistentIsolateData() {

lib/ui/window/platform_configuration.h

@@ -30,7 +30,7 @@ class Scene;
 /// @brief An enum for defining the different kinds of accessibility features
 ///        that can be enabled by the platform.
 ///
-///         Must match the `AccessibilityFeatureFlag` enum in framework.
+///         Must match the `AccessibilityFeatures` class in framework.
 enum class AccessibilityFeatureFlag : int32_t {
   kAccessibleNavigation = 1 << 0,
   kInvertColors = 1 << 1,
@@ -538,7 +538,7 @@ class PlatformConfigurationNativeApi {
   static void RegisterBackgroundIsolate(int64_t root_isolate_token);
 
  private:
-  static Dart_PerformanceMode current_performace_mode_;
+  static Dart_PerformanceMode current_performance_mode_;
 };
 
 }  // namespace flutter

shell/platform/common/application_lifecycle.cc

@@ -0,0 +1,29 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/common/application_lifecycle.h"
+
+#include <cassert>
+
+namespace flutter {
+
+const char* AppLifecycleStateToString(AppLifecycleState state) {
+  switch (state) {
+    case kAppLifecycleStateDetached:
+      return "AppLifecycleState.detached";
+    case kAppLifecycleStateResumed:
+      return "AppLifecycleState.resumed";
+    case kAppLifecycleStateInactive:
+      return "AppLifecycleState.inactive";
+    case kAppLifecycleStateHidden:
+      return "AppLifecycleState.hidden";
+    case kAppLifecycleStatePaused:
+      return "AppLifecycleState.paused";
+    default:
+      assert(false && "Lifecycle state not recognized");
+      break;
+  }
+}
+
+}  // namespace flutter

shell/platform/common/application_lifecycle.h

@@ -0,0 +1,64 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_COMMON_APPLICATION_LIFECYCLE_H_
+#define FLUTTER_SHELL_PLATFORM_COMMON_APPLICATION_LIFECYCLE_H_
+
+namespace flutter {
+
+/// This enum describes the possible lifecycle states of the application. It
+/// must be kept up to date with changes in the framework's AppLifecycleState
+/// enum. It is passed to the embedder's |SetLifecycleState| function.
+///
+/// |SetLifecycleState| will validate that the state transition is a valid state
+/// transition, and will assert if it is not. States not supported on a platform
+/// will be emitted when transitioning between states which are supported, so
+/// that all implementations share the same allowed state machine. Here is the
+/// allowed state machine:
+///
+///             +-----------+                               +-----------+
+///             | detached  |------------------------------>|  resumed  |
+///             +-----------+                               +-----------+
+///                  ^                                              ^
+///                  |                                              |
+///                  |                                              v
+///             +-----------+        +--------------+       +-----------+
+///             | paused    |<------>|    hidden    |<----->|  inactive |
+///             +-----------+        +--------------+       +-----------+
+///
+/// The states and their meanings are as follows:
+///
+/// detached: The initial state of the state machine. On Android and iOS,
+///           also the final state of the state machine when all views are
+///           detached. Other platforms do not enter this state again after
+///           initially leaving it.
+///
+/// resumed: The nominal "running" state of the application. The
+///          application is visible, has input focus, and is running.
+///
+/// inactive: At least one view of the application is visible, but none
+///           have input focus. The application is otherwise running
+///           normally.
+///
+/// hidden: All views of an application are hidden, either because the
+///         application is being stopped (on iOS and Android), or because
+///         it is being minimized or on a desktop that is no longer visible
+///         (on desktop), or on a tab that is no longer visible (on web).
+///
+/// paused: The application is not running, and can be detached or started
+///         again at any time. This state is typically only entered into on
+///         iOS and Android.
+typedef enum {
+  kAppLifecycleStateDetached = 0x0,
+  kAppLifecycleStateResumed = 0x1,
+  kAppLifecycleStateInactive = 0x2,
+  kAppLifecycleStateHidden = 0x3,
+  kAppLifecycleStatePaused = 0x4,
+} AppLifecycleState;
+
+const char* AppLifecycleStateToString(AppLifecycleState state);
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_COMMON_APPLICATION_LIFECYCLE_H_

shell/platform/common/client_wrapper/include/flutter/plugin_registrar.h

@@ -49,8 +49,8 @@ class PluginRegistrar {
   // Takes ownership of |plugin|.
   //
   // Plugins are not required to call this method if they have other lifetime
-  // management, but this is a convient place for plugins to be owned to ensure
-  // that they stay valid for any registered callbacks.
+  // management, but this is a convenient place for plugins to be owned to
+  // ensure that they stay valid for any registered callbacks.
   void AddPlugin(std::unique_ptr<Plugin> plugin);
 
  protected:

shell/platform/darwin/ios/framework/Headers/FlutterPlugin.h

@@ -28,15 +28,15 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * Called if this has been registered for `UIApplicationDelegate` callbacks.
  *
- * @return `NO` if this vetoes application launch.
+ * @return `NO` if this vetos application launch.
  */
 - (BOOL)application:(UIApplication*)application
     didFinishLaunchingWithOptions:(NSDictionary*)launchOptions;
 
 /**
  * Called if this has been registered for `UIApplicationDelegate` callbacks.
  *
- * @return `NO` if this vetoes application launch.
+ * @return `NO` if this vetos application launch.
  */
 - (BOOL)application:(UIApplication*)application
     willFinishLaunchingWithOptions:(NSDictionary*)launchOptions;

shell/platform/darwin/ios/framework/Headers/FlutterPluginAppLifeCycleDelegate.h

@@ -16,25 +16,25 @@ FLUTTER_DARWIN_EXPORT
 @interface FlutterPluginAppLifeCycleDelegate : NSObject <UNUserNotificationCenterDelegate>
 
 /**
- * Registers `delegate` to receive life cycle callbacks via this FlutterPluginAppLifecycleDelegate
+ * Registers `delegate` to receive life cycle callbacks via this FlutterPluginAppLifeCycleDelegate
  * as long as it is alive.
  *
- * `delegate` will only referenced weakly.
+ * `delegate` will only be referenced weakly.
  */
 - (void)addDelegate:(NSObject<FlutterApplicationLifeCycleDelegate>*)delegate;
 
 /**
  * Calls all plugins registered for `UIApplicationDelegate` callbacks.
  *
- * @return `NO` if any plugin vetoes application launch.
+ * @return `NO` if any plugin vetos application launch.
  */
 - (BOOL)application:(UIApplication*)application
     didFinishLaunchingWithOptions:(NSDictionary*)launchOptions;
 
 /**
  * Calls all plugins registered for `UIApplicationDelegate` callbacks.
  *
- * @return `NO` if any plugin vetoes application launch.
+ * @return `NO` if any plugin vetos application launch.
  */
 - (BOOL)application:(UIApplication*)application
     willFinishLaunchingWithOptions:(NSDictionary*)launchOptions;

shell/platform/darwin/macos/BUILD.gn

@@ -38,6 +38,7 @@ _framework_binary_subpath = "Versions/A/$_flutter_framework_name"
 # the Flutter engine source root.
 _flutter_framework_headers = [
   "framework/Headers/FlutterAppDelegate.h",
+  "framework/Headers/FlutterAppLifecycleDelegate.h",
   "framework/Headers/FlutterDartProject.h",
   "framework/Headers/FlutterEngine.h",
   "framework/Headers/FlutterMacOS.h",
@@ -57,6 +58,7 @@ source_set("flutter_framework_source") {
     "framework/Source/AccessibilityBridgeMac.h",
     "framework/Source/AccessibilityBridgeMac.mm",
     "framework/Source/FlutterAppDelegate.mm",
+    "framework/Source/FlutterAppLifecycleDelegate.mm",
     "framework/Source/FlutterBackingStore.h",
     "framework/Source/FlutterBackingStore.mm",
     "framework/Source/FlutterChannelKeyResponder.h",

shell/platform/darwin/macos/framework/Headers/FlutterAppLifecycleDelegate.h

@@ -0,0 +1,128 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_FLUTTERAPPLIFECYCLEDELEGATE_H_
+#define FLUTTER_FLUTTERAPPLIFECYCLEDELEGATE_H_
+
+#import <Cocoa/Cocoa.h>
+#include <Foundation/Foundation.h>
+
+#import "FlutterMacros.h"
+#import "FlutterPluginMacOS.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+#pragma mark -
+/**
+ * Protocol for listener of events from the NSApplication, typically a
+ * FlutterPlugin.
+ */
+@protocol FlutterAppLifecycleDelegate <NSObject>
+
+@optional
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationWillFinishLaunching
+ * notification.
+ */
+- (void)handleWillFinishLaunching:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationDidFinishLaunching
+ * notification.
+ */
+- (void)handleDidFinishLaunching:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationWillBecomeActive
+ * notification.
+ */
+- (void)handleWillBecomeActive:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationDidBecomeActive
+ * notification.
+ */
+- (void)handleDidBecomeActive:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationWillResignActive
+ * notification.
+ */
+- (void)handleWillResignActive:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationWillResignActive
+ * notification.
+ */
+- (void)handleDidResignActive:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationWillHide
+ * notification.
+ */
+- (void)handleWillHide:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationDidHide
+ * notification.
+ */
+- (void)handleDidHide:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationWillUnhide
+ * notification.
+ */
+- (void)handleWillUnhide:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationDidUnhide
+ * notification.
+ */
+- (void)handleDidUnhide:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationDidUnhide
+ * notification.
+ */
+- (void)handleDidChangeScreenParameters:(NSNotification*)notification;
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationDidUnhide
+ * notification.
+ */
+- (void)handleDidChangeOcclusionState:(NSNotification*)notification API_AVAILABLE(macos(10.9));
+
+/**
+ * Called when the |FlutterAppDelegate| gets the applicationWillTerminate
+ * notification.
+ */
+- (void)handleWillTerminate:(NSNotification*)notification;
+@end
+
+#pragma mark -
+
+/**
+ * Propagates `NSAppDelegate` callbacks to registered plugins.
+ */
+FLUTTER_DARWIN_EXPORT
+@interface FlutterAppLifecycleRegistrar : NSObject <FlutterAppLifecycleDelegate>
+
+/**
+ * Registers `delegate` to receive life cycle callbacks via this FlutterAppLifecycleDelegate
+ * as long as it is alive.
+ *
+ * `delegate` will only be referenced weakly.
+ */
+- (void)addDelegate:(NSObject<FlutterAppLifecycleDelegate>*)delegate;
+
+/**
+ * Unregisters `delegate` so that it will no longer receive life cycle callbacks
+ * via this FlutterAppLifecycleDelegate.
+ */
+- (void)removeDelegate:(NSObject<FlutterAppLifecycleDelegate>*)delegate;
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif  // FLUTTER_FLUTTERAPPLIFECYCLEDELEGATE_H_