Support hot reload for applications that don't use the framework (#5868)

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

@@ -107,6 +107,10 @@ abstract class BindingBase {
       name: 'exit',
       callback: _exitApplication
     );
+    registerSignalServiceExtension(
+      name: 'frameworkPresent',
+      callback: () => null
+    );
     assert(() { _debugServiceExtensionsRegistered = true; return true; });
   }
 
@@ -124,6 +128,7 @@ abstract class BindingBase {
     FlutterError.resetErrorCount();
   }
 
+
   /// Registers a service extension method with the given name (full
   /// name "ext.flutter.name"), which takes no arguments and returns
   /// no value.

packages/flutter_tools/lib/src/hot.dart

@@ -414,19 +414,25 @@ class HotRunner extends ResidentRunner {
     firstFrameTimer.start();
     await _updateDevFS();
     await _launchFromDevFS(_package, _mainPath);
+    bool waitForFrame =
+        await currentView.uiIsolate.flutterFrameworkPresent();
     Status restartStatus =
         logger.startProgress('Waiting for application to start...');
-    // Wait for the first frame to be rendered.
-    await firstFrameTimer.firstFrame();
+    if (waitForFrame) {
+      // Wait for the first frame to be rendered.
+      await firstFrameTimer.firstFrame();
+    }
     restartStatus.stop(showElapsedTime: true);
-    printStatus('Restart time: '
-                '${getElapsedAsMilliseconds(firstFrameTimer.elapsed)}');
-    if (benchmarkMode) {
-      benchmarkData['hotRestartMillisecondsToFrame'] =
-          firstFrameTimer.elapsed.inMilliseconds;
+    if (waitForFrame) {
+      printStatus('Restart time: '
+                  '${getElapsedAsMilliseconds(firstFrameTimer.elapsed)}');
+      if (benchmarkMode) {
+        benchmarkData['hotRestartMillisecondsToFrame'] =
+            firstFrameTimer.elapsed.inMilliseconds;
+      }
+      flutterUsage.sendTiming('hot', 'restart', firstFrameTimer.elapsed);
     }
     flutterUsage.sendEvent('hot', 'restart');
-    flutterUsage.sendTiming('hot', 'restart', firstFrameTimer.elapsed);
   }
 
   /// Returns [true] if the reload was successful.
@@ -489,22 +495,33 @@ class HotRunner extends ResidentRunner {
     await _evictDirtyAssets();
     Status reassembleStatus =
         logger.startProgress('Reassembling application...');
+    bool waitForFrame = true;
     try {
-      await currentView.uiIsolate.flutterReassemble();
+      waitForFrame = (await currentView.uiIsolate.flutterReassemble() != null);
     } catch (_) {
       reassembleStatus.stop(showElapsedTime: true);
       printError('Reassembling application failed.');
       return false;
     }
     reassembleStatus.stop(showElapsedTime: true);
-    await firstFrameTimer.firstFrame();
-    printStatus('Hot reload time: '
-                '${getElapsedAsMilliseconds(firstFrameTimer.elapsed)}');
-    if (benchmarkMode) {
-      benchmarkData['hotReloadMillisecondsToFrame'] =
-          firstFrameTimer.elapsed.inMilliseconds;
+    try {
+      /* ensure that a frame is scheduled */
+      await currentView.uiIsolate.uiWindowScheduleFrame();
+    } catch (_) {
+      /* ignore any errors */
+    }
+    if (waitForFrame) {
+      // When the framework is present, we can wait for the first frame
+      // event and measure reload itme.
+      await firstFrameTimer.firstFrame();
+      printStatus('Hot reload time: '
+                  '${getElapsedAsMilliseconds(firstFrameTimer.elapsed)}');
+      if (benchmarkMode) {
+        benchmarkData['hotReloadMillisecondsToFrame'] =
+            firstFrameTimer.elapsed.inMilliseconds;
+      }
+      flutterUsage.sendTiming('hot', 'reload', firstFrameTimer.elapsed);
     }
-    flutterUsage.sendTiming('hot', 'reload', firstFrameTimer.elapsed);
     return true;
   }
 

packages/flutter_tools/lib/src/resident_runner.dart

@@ -56,7 +56,7 @@ abstract class ResidentRunner {
   Future<Null> _debugDumpRenderTree() async {
     if (vmService != null)
       await vmService.vm.refreshViews();
-    
+
     await currentView.uiIsolate.flutterDebugDumpRenderTree();
   }
 

packages/flutter_tools/lib/src/vmservice.dart

@@ -7,6 +7,7 @@ import 'dart:convert' show BASE64;
 import 'dart:io';
 
 import 'package:json_rpc_2/json_rpc_2.dart' as rpc;
+import 'package:json_rpc_2/error_code.dart' as rpc_error_code;
 import 'package:web_socket_channel/io.dart';
 
 import 'globals.dart';
@@ -766,12 +767,28 @@ class Isolate extends ServiceObjectOwner {
 
   // Flutter extension methods.
 
+  // Invoke a flutter extension method, if the flutter extension is not
+  // available, returns null.
+  Future<Map<String, dynamic>> invokeFlutterExtensionRpcRaw(
+      String method, [Map<String, dynamic> params]) async {
+    try {
+      return await invokeRpcRaw(method, params);
+    } catch (e) {
+      // If an application is not using the framework
+      if (_isMethodNotFoundException(e))
+        return null;
+      rethrow;
+    }
+  }
+
+  // Debug dump extension methods.
+
   Future<Map<String, dynamic>> flutterDebugDumpApp() {
-    return invokeRpcRaw('ext.flutter.debugDumpApp');
+    return invokeFlutterExtensionRpcRaw('ext.flutter.debugDumpApp');
   }
 
   Future<Map<String, dynamic>> flutterDebugDumpRenderTree() {
-    return invokeRpcRaw('ext.flutter.debugDumpRenderTree');
+    return invokeFlutterExtensionRpcRaw('ext.flutter.debugDumpRenderTree');
   }
 
   // Loader page extension methods.
@@ -797,20 +814,36 @@ class Isolate extends ServiceObjectOwner {
     }).catchError((dynamic error) => null);
   }
 
-  /// Causes the application to pick up any changed code.
-  Future<Map<String, dynamic>> flutterReassemble() {
-    return invokeRpcRaw('ext.flutter.reassemble');
+  static bool _isMethodNotFoundException(dynamic e) {
+    return (e is rpc.RpcException) &&
+           (e.code == rpc_error_code.METHOD_NOT_FOUND);
   }
 
-  Future<Map<String, dynamic>> flutterEvictAsset(String assetPath) {
-    return invokeRpcRaw('ext.flutter.evict', <String, dynamic>{
-      'value': assetPath
-    });
+  // Reload related extension methods.
+  Future<Map<String, dynamic>> flutterReassemble() async {
+    return await invokeFlutterExtensionRpcRaw('ext.flutter.reassemble');
+  }
+
+  Future<bool> flutterFrameworkPresent() async {
+    return (await invokeFlutterExtensionRpcRaw('ext.flutter.frameworkPresent') != null);
+  }
+
+  Future<Map<String, dynamic>> uiWindowScheduleFrame() async {
+    return await invokeFlutterExtensionRpcRaw('ext.ui.window.scheduleFrame');
+  }
+
+  Future<Map<String, dynamic>> flutterEvictAsset(String assetPath) async {
+    return await invokeFlutterExtensionRpcRaw('ext.flutter.evict',
+        <String, dynamic>{
+          'value': assetPath
+        }
+    );
   }
 
-  Future<Map<String, dynamic>> flutterExit() {
-    return invokeRpcRaw('ext.flutter.exit').timeout(
-        const Duration(seconds: 2), onTimeout: () => null);
+  // Application control extension methods.
+  Future<Map<String, dynamic>> flutterExit() async {
+    return await invokeFlutterExtensionRpcRaw('ext.flutter.exit').timeout(
+          const Duration(seconds: 2), onTimeout: () => null);
   }
 }