Implement a protocol for discovering active Flutter instances on Android (#2720)

Tools can send a broadcast intent that will cause Flutter processes to
write their names and observatory ports to the log in JSON format.

sky/engine/core/script/dart_service_isolate.cc

@@ -7,6 +7,7 @@
 #include "base/logging.h"
 #include "dart/runtime/include/dart_api.h"
 #include "sky/engine/core/script/embedder_resources.h"
+#include "sky/engine/tonic/dart_converter.h"
 #include "sky/engine/tonic/dart_error.h"
 #include "sky/engine/tonic/dart_library_natives.h"
 
@@ -38,6 +39,7 @@ namespace {
 static Dart_LibraryTagHandler g_embedder_tag_handler;
 static DartLibraryNatives* g_natives;
 static EmbedderResources* g_resources;
+static int observatory_port_;
 
 Dart_NativeFunction GetNativeFunction(Dart_Handle name,
                                       int argument_count,
@@ -61,7 +63,15 @@ void DartServiceIsolate::TriggerResourceLoad(Dart_NativeArguments args) {
 }
 
 void DartServiceIsolate::NotifyServerState(Dart_NativeArguments args) {
-  // NO-OP.
+  Dart_Handle exception = nullptr;
+  int port = DartConverter<int>::FromArguments(args, 1, exception);
+  if (!exception) {
+    observatory_port_ = port;
+  }
+}
+
+int DartServiceIsolate::GetObservatoryPort() {
+  return observatory_port_;
 }
 
 void DartServiceIsolate::Shutdown(Dart_NativeArguments args) {

sky/engine/core/script/dart_service_isolate.h

@@ -21,6 +21,8 @@ class DartServiceIsolate {
                       bool running_precompiled,
                       char** error);
 
+  static int GetObservatoryPort();
+
  private:
   // Native entries.
   static void TriggerResourceLoad(Dart_NativeArguments args);

sky/shell/platform/android/io/flutter/view/FlutterView.java

@@ -5,7 +5,11 @@
 package io.flutter.view;
 
 import android.app.Activity;
+import android.content.BroadcastReceiver;
 import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.pm.ApplicationInfo;
 import android.content.res.Configuration;
 import android.opengl.Matrix;
 import android.graphics.Rect;
@@ -24,6 +28,8 @@ import android.view.accessibility.AccessibilityNodeInfo;
 import android.view.accessibility.AccessibilityNodeProvider;
 import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
+import org.json.JSONException;
+import org.json.JSONObject;
 
 import org.chromium.base.JNINamespace;
 import org.chromium.mojo.bindings.Interface.Binding;
@@ -68,6 +74,8 @@ public class FlutterView extends SurfaceView
              AccessibilityManager.TouchExplorationStateChangeListener {
     private static final String TAG = "FlutterView";
 
+    private static final String ACTION_DISCOVER = "io.flutter.view.DISCOVER";
+
     private long mNativePlatformView;
     private SkyEngine.Proxy mSkyEngine;
     private ServiceProviderImpl mPlatformServiceProvider;
@@ -83,6 +91,7 @@ public class FlutterView extends SurfaceView
     private final KeyboardViewState mKeyboardState;
     private final RawKeyboardServiceState mRawKeyboardState;
     private final AccessibilityManager mAccessibilityManager;
+    private BroadcastReceiver discoveryReceiver;
 
     public FlutterView(Context context) {
         this(context, null);
@@ -139,6 +148,11 @@ public class FlutterView extends SurfaceView
         mAsyncOnMessageListeners = new HashMap<String, OnMessageListenerAsync>();
 
         setLocale(getResources().getConfiguration().locale);
+
+        if ((context.getApplicationInfo().flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
+            discoveryReceiver = new DiscoveryReceiver();
+            context.registerReceiver(discoveryReceiver, new IntentFilter(ACTION_DISCOVER));
+        }
     }
 
     @Override
@@ -193,6 +207,10 @@ public class FlutterView extends SurfaceView
     }
 
     public void destroy() {
+        if (discoveryReceiver != null) {
+            getContext().unregisterReceiver(discoveryReceiver);
+        }
+
         if (mPlatformServiceProviderBinding != null) {
             mPlatformServiceProviderBinding.unbind().close();
             mPlatformServiceProvider.unbindServices();
@@ -439,6 +457,7 @@ public class FlutterView extends SurfaceView
     }
 
     private static native long nativeAttach(int inputObserverHandle);
+    private static native int nativeGetObservatoryPort();
     private static native void nativeDetach(long nativePlatformViewAndroid);
     private static native void nativeSurfaceCreated(long nativePlatformViewAndroid,
                                                     Surface surface);
@@ -647,4 +666,17 @@ public class FlutterView extends SurfaceView
             callback.call(reply);
         }
     }
+
+    /** Broadcast receiver used to discover active Flutter instances. */
+    private class DiscoveryReceiver extends BroadcastReceiver {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            JSONObject discover = new JSONObject();
+            try {
+                discover.put("id", getContext().getPackageName());
+                discover.put("observatoryPort", nativeGetObservatoryPort());
+                Log.i(TAG, "DISCOVER: " + discover);
+            } catch (JSONException e) {}
+        }
+    }
 }

sky/shell/platform/android/platform_view_android.cc

@@ -11,6 +11,7 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "jni/FlutterView_jni.h"
+#include "sky/engine/core/script/dart_service_isolate.h"
 #include "sky/shell/gpu/direct/surface_notifications_direct.h"
 #include "sky/shell/shell.h"
 #include "sky/shell/shell_view.h"
@@ -28,6 +29,10 @@ static jlong Attach(JNIEnv* env, jclass clazz, jint skyEngineHandle) {
   return reinterpret_cast<jlong>(shell_view->view());
 }
 
+jint GetObservatoryPort(JNIEnv* env, jclass clazz) {
+  return blink::DartServiceIsolate::GetObservatoryPort();
+}
+
 // static
 bool PlatformViewAndroid::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);