Support dynamic registration of mojo services on Android

SkyApplication now reads service info from a services.json file bundled
with the apk. For each service, it registers a method that invokes
connectToService on a named class. This way, third party services can
register themselves.

There's a corresponding change to flutter_tools to generate this
services.json when building an apk that depends on services.

build/config/android/rules.gni

@@ -1577,7 +1577,7 @@ template("android_apk") {
   }
 
   final_deps += [ ":$final_dex_target_name" ]
-  dex("$final_dex_target_name") {
+  dex("${final_dex_target_name}_jar") {
     deps = [
       ":$build_config_target",
       ":$java_target",
@@ -1588,11 +1588,21 @@ template("android_apk") {
     inputs = [
       _build_config,
     ]
-    output = final_dex_path
+    output = "${final_dex_path}.jar"
     dex_arg_key = "${_rebased_build_config}:final_dex:dependency_dex_files"
     args = [ "--inputs=@FileArg($dex_arg_key)" ]
   }
 
+  dex("$final_dex_target_name") {
+    deps = [
+      ":${final_dex_target_name}_jar",
+    ]
+    sources = [
+      "${final_dex_path}.jar",
+    ]
+    output = final_dex_path
+  }
+
   if (_native_libs != []) {
     action("${_template_name}__prepare_native") {
       script = "//build/android/gyp/pack_relocations.py"

sky/BUILD.gn

@@ -28,9 +28,17 @@ group("sky") {
 
   if (is_android) {
     deps += [ "//sky/services/activity" ]
+
+    # TODO(mpcomplete): This is temporary until we move GCM out of the engine
+    # repo.
+    deps += [
+      "//sky/services/gcm:gcm_lib",
+      "//sky/services/gcm:interfaces_java",
+    ]
   }
 
   if (!is_android) {
     deps += [ "//third_party/mesa:osmesa" ]
   }
+
 }

sky/services/gcm/src/org/domokit/gcm/RegistrationIntentService.java

@@ -16,6 +16,8 @@
 import java.io.IOException;
 
 import org.chromium.base.ThreadUtils;
+import org.chromium.mojo.system.Core;
+import org.chromium.mojo.system.MessagePipeHandle;
 import org.chromium.mojo.system.MojoException;
 import org.chromium.mojom.gcm.GcmListener;
 import org.chromium.mojom.gcm.GcmService;
@@ -37,6 +39,10 @@ public MojoService(Context context) {
             this.context = context;
         }
 
+        public static void connectToService(Context context, Core core, MessagePipeHandle pipe) {
+            GcmService.MANAGER.bind(new MojoService(context), pipe);
+        }
+
         @Override
         public void close() {}
 

sky/shell/platform/android/org/domokit/sky/shell/SkyApplication.java

@@ -5,7 +5,15 @@
 package org.domokit.sky.shell;
 
 import android.content.Context;
+import android.content.res.AssetManager;
 import android.util.Log;
+import java.io.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.InputStreamReader;
+import java.io.IOException;
+import org.json.JSONArray;
+import org.json.JSONObject;
+import org.json.JSONTokener;
 
 import org.chromium.base.BaseChromiumApplication;
 import org.chromium.base.library_loader.LibraryLoader;
@@ -35,6 +43,7 @@
 public class SkyApplication extends BaseChromiumApplication {
     static final String APP_BUNDLE = "app.flx";
     static final String MANIFEST = "flutter.yaml";
+    static final String SERVICES = "services.json";
 
     private static final String TAG = "SkyApplication";
     private static final String PRIVATE_DATA_DIRECTORY_SUFFIX = "sky_shell";
@@ -67,6 +76,8 @@ protected void onBeforeResourceExtraction(ResourceExtractor extractor) {
       * Override this function to register more services.
       */
     protected void onServiceRegistryAvailable(ServiceRegistry registry) {
+        parseServicesConfig(registry);
+
         registry.register(Activity.MANAGER.getName(), new ServiceFactory() {
             @Override
             public void connectToService(Context context, Core core, MessagePipeHandle pipe) {
@@ -119,6 +130,55 @@ public void connectToService(Context context, Core core, MessagePipeHandle pipe)
         });
     }
 
+    /**
+     * Parses the auto-generated services.json file, which contains additional services to register.
+     */
+    private void parseServicesConfig(ServiceRegistry registry) {
+        final AssetManager manager = getResources().getAssets();
+        try (BufferedReader reader = new BufferedReader(new InputStreamReader(manager.open(SERVICES)))) {
+            StringBuffer json = new StringBuffer();
+            while (true) {
+              String line = reader.readLine();
+              if (line == null)
+                  break;
+              json.append(line);
+            }
+
+            JSONObject object = (JSONObject) new JSONTokener(json.toString()).nextValue();
+            JSONArray services = object.getJSONArray("services");
+            for (int i = 0; i < services.length(); ++i) {
+                JSONObject service = services.getJSONObject(i);
+                String serviceName = service.getString("name");
+                String className = service.getString("class");
+                registerService(registry, serviceName, className);
+            }
+        } catch (FileNotFoundException e) {
+            // Not all apps will have a services.json file.
+            return;
+        } catch (Exception e) {
+            Log.e(TAG, "Failure parsing service configuration file", e);
+            return;
+        }
+    }
+
+    /**
+     * Registers a third-party service.
+     */
+    private void registerService(ServiceRegistry registry, final String serviceName, final String className) {
+        registry.register(serviceName, new ServiceFactory() {
+            @Override
+            public void connectToService(Context context, Core core, MessagePipeHandle pipe) {
+                try {
+                    Class.forName(className)
+                        .getMethod("connectToService", Context.class, Core.class, MessagePipeHandle.class)
+                        .invoke(null, context, core, pipe);
+                } catch(Exception e) {
+                    Log.e(TAG, "Failed to register service '" + serviceName + "'", e);
+                }
+            }
+        });
+    }
+
     private void initJavaUtils() {
         PathUtils.setPrivateDataDirectorySuffix(PRIVATE_DATA_DIRECTORY_SUFFIX,
                                                 getApplicationContext());

sky/tools/release_engine.py

@@ -48,8 +48,10 @@ def git_revision(cwd):
         'icudtl.dat',
         'dist/shell/SkyShell.apk',
         'dist/shell/flutter.mojo',
-        'gen/sky/shell/shell/classes.dex',
+        'gen/sky/shell/shell/classes.dex.jar',
         'gen/sky/shell/shell/shell/libs/armeabi-v7a/libsky_shell.so',
+        # TODO(mpcomplete): obsolete. Remove after updating the flutter tool.
+        'gen/sky/shell/shell/classes.dex',
     ],
     'linux-x64': [
         'dist/shell/icudtl.dat',