Add `profilePlatformChannels` service extension (#136051)

We will expose this from a button in DevTools.
https://github.com/flutter/devtools/issues/6166

packages/flutter/lib/src/services/binding.dart

@@ -12,8 +12,10 @@ import 'package:flutter/scheduler.dart';
 
 import 'asset_bundle.dart';
 import 'binary_messenger.dart';
+import 'debug.dart';
 import 'hardware_keyboard.dart';
 import 'message_codec.dart';
+import 'platform_channel.dart';
 import 'restoration.dart';
 import 'service_extensions.dart';
 import 'system_channels.dart';
@@ -224,6 +226,16 @@ mixin ServicesBinding on BindingBase, SchedulerBinding {
       );
       return true;
     }());
+
+    if (!kReleaseMode) {
+      registerBoolServiceExtension(
+        name: ServicesServiceExtensions.profilePlatformChannels.name,
+        getter: () async => debugProfilePlatformChannels,
+        setter: (bool value) async {
+          debugProfilePlatformChannels = value;
+        },
+      );
+    }
   }
 
   /// Called in response to the `ext.flutter.evict` service extension.

packages/flutter/lib/src/services/debug.dart

@@ -41,3 +41,17 @@ bool debugAssertAllServicesVarsUnset(String reason) {
   }());
   return true;
 }
+
+/// Controls whether platform channel usage can be debugged in non-release mode.
+///
+/// This value is modified by calls to the
+/// [ServicesServiceExtensions.profilePlatformChannels] service extension.
+///
+/// See also:
+///
+/// * [shouldProfilePlatformChannels], which checks both
+///   [kProfilePlatformChannels] and [debugProfilePlatformChannels] for the
+///   current run mode.
+/// * [kProfilePlatformChannels], which determines whether platform channel
+///   usage can be debugged in release mode.
+bool debugProfilePlatformChannels = false;

packages/flutter/lib/src/services/platform_channel.dart

@@ -12,6 +12,7 @@ import '_background_isolate_binary_messenger_io.dart'
 
 import 'binary_messenger.dart';
 import 'binding.dart';
+import 'debug.dart';
 import 'message_codec.dart';
 import 'message_codecs.dart';
 
@@ -32,6 +33,17 @@ export 'message_codec.dart' show MessageCodec, MethodCall, MethodCodec;
 /// The statistics include the total bytes transmitted and the average number of
 /// bytes per invocation in the last quantum. "Up" means in the direction of
 /// Flutter to the host platform, "down" is the host platform to flutter.
+bool get shouldProfilePlatformChannels => kProfilePlatformChannels || (!kReleaseMode && debugProfilePlatformChannels);
+
+/// Controls whether platform channel usage can be debugged in release mode.
+///
+/// See also:
+///
+/// * [shouldProfilePlatformChannels], which checks both
+///   [kProfilePlatformChannels] and [debugProfilePlatformChannels] for the
+///   current run mode.
+/// * [debugProfilePlatformChannels], which determines whether platform
+///   channel usage can be debugged in non-release mode.
 const bool kProfilePlatformChannels = false;
 
 bool _profilePlatformChannelsIsRunning = false;
@@ -190,7 +202,7 @@ class BasicMessageChannel<T> {
   /// [BackgroundIsolateBinaryMessenger.ensureInitialized].
   BinaryMessenger get binaryMessenger {
     final BinaryMessenger result = _binaryMessenger ?? _findBinaryMessenger();
-    return kProfilePlatformChannels
+    return shouldProfilePlatformChannels
         ? _profiledBinaryMessengers[this] ??= _ProfiledBinaryMessenger(
             // ignore: no_runtimetype_tostring
             result, runtimeType.toString(), codec.runtimeType.toString())
@@ -279,7 +291,7 @@ class MethodChannel {
   /// [BackgroundIsolateBinaryMessenger.ensureInitialized].
   BinaryMessenger get binaryMessenger {
     final BinaryMessenger result = _binaryMessenger ?? _findBinaryMessenger();
-    return kProfilePlatformChannels
+    return shouldProfilePlatformChannels
         ? _profiledBinaryMessengers[this] ??= _ProfiledBinaryMessenger(
             // ignore: no_runtimetype_tostring
             result, runtimeType.toString(), codec.runtimeType.toString())
@@ -310,7 +322,7 @@ class MethodChannel {
   Future<T?> _invokeMethod<T>(String method, { required bool missingOk, dynamic arguments }) async {
     final ByteData input = codec.encodeMethodCall(MethodCall(method, arguments));
     final ByteData? result =
-      kProfilePlatformChannels ?
+      shouldProfilePlatformChannels ?
         await (binaryMessenger as _ProfiledBinaryMessenger).sendWithPostfix(name, '#$method', input) :
         await binaryMessenger.send(name, input);
     if (result == null) {

packages/flutter/lib/src/services/service_extensions.dart

@@ -11,6 +11,19 @@
 /// The String value for each of these extension names should be accessed by
 /// calling the `.name` property on the enum value.
 enum ServicesServiceExtensions {
+  /// Name of service extension that, when called, will toggle whether
+  /// statistics about the usage of Platform Channels will be printed out
+  /// periodically to the console and Timeline events will show the time between
+  /// sending and receiving a message (encoding and decoding time excluded).
+  ///
+  /// See also:
+  ///
+  /// * [debugProfilePlatformChannels], which is the flag that this service
+  ///   extension exposes.
+  /// * [ServicesBinding.initServiceExtensions], where the service extension is
+  ///   registered.
+  profilePlatformChannels,
+
   /// Name of service extension that, when called, will evict an image from the
   /// rootBundle cache and cause the image cache to be cleared.
   ///

packages/flutter/test/foundation/service_extensions_test.dart

@@ -183,7 +183,7 @@ void main() {
     // framework, excluding any that are for the widget inspector (see
     // widget_inspector_test.dart for tests of the ext.flutter.inspector service
     // extensions). Any test counted here must be tested in this file!
-    const int serviceExtensionCount = 29;
+    const int serviceExtensionCount = 30;
 
     expect(binding.extensions.length, serviceExtensionCount + widgetInspectorExtensionCount - disabledExtensions);
     expect(testedExtensions, hasLength(serviceExtensionCount));
@@ -597,6 +597,34 @@ void main() {
     testedExtensions.add(RenderingServiceExtensions.profileRenderObjectLayouts.name);
   });
 
+  test('Service extensions - profilePlatformChannels', () async {
+    Map<String, dynamic> result;
+
+    expect(debugProfilePlatformChannels, false);
+
+    result = await binding.testExtension(ServicesServiceExtensions.profilePlatformChannels.name, <String, String>{});
+    expect(result, <String, String>{'enabled': 'false'});
+    expect(debugProfilePlatformChannels, false);
+
+    result = await binding.testExtension(ServicesServiceExtensions.profilePlatformChannels.name, <String, String>{'enabled': 'true'});
+    expect(result, <String, String>{'enabled': 'true'});
+    expect(debugProfilePlatformChannels, true);
+
+    result = await binding.testExtension(ServicesServiceExtensions.profilePlatformChannels.name, <String, String>{});
+    expect(result, <String, String>{'enabled': 'true'});
+    expect(debugProfilePlatformChannels, true);
+
+    result = await binding.testExtension(ServicesServiceExtensions.profilePlatformChannels.name, <String, String>{'enabled': 'false'});
+    expect(result, <String, String>{'enabled': 'false'});
+    expect(debugProfilePlatformChannels, false);
+
+    result = await binding.testExtension(ServicesServiceExtensions.profilePlatformChannels.name, <String, String>{});
+    expect(result, <String, String>{'enabled': 'false'});
+    expect(debugProfilePlatformChannels, false);
+
+    testedExtensions.add(ServicesServiceExtensions.profilePlatformChannels.name);
+  });
+
   test('Service extensions - evict', () async {
     Map<String, dynamic> result;
     bool completed;