[Bundles] Add module_installer_backend.cc with native OnInstallModule handler.

To prepare for handling native resource loading after DFM installation,
this CL adds a new hook in ModuleInstallerBackend.onFinished() to call
(via JNI) a new native handler for each newly installed module:
  JNI_ModuleInstallerBackend_OnInstallModule()

AsyncTask is used to make the JNI call asynchronous, taking place
outside the UI thread. This allows file access (e.g., to open native
resources) to take place in the native code, thereby preventing
assert failure in Debug builds.

After the JNI call, |mListener.onFinished()| is called on UI thread,
just like before.

Bug: 927131
Change-Id: I36880cc7739a48534052b51d3d655d1ae0beb29a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1702905
Commit-Queue: Samuel Huang <huangs@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680452}

chrome/browser/BUILD.gn

@@ -2839,6 +2839,7 @@ jumbo_split_static_library("browser") {
       "//components/feed:feature_list",
       "//components/invalidation/impl:feature_list",
       "//components/language/android:language_bridge",
+      "//components/module_installer/android:module_installer",
       "//components/omnibox/browser",
       "//components/payments/content/android",
       "//components/resources:components_resources",

components/module_installer/android/BUILD.gn

@@ -50,6 +50,22 @@ android_library("module_installer_impl_java") {
   ]
 }
 
+generate_jni("module_installer_jni_headers") {
+  sources = [
+    "java/src-impl/org/chromium/components/module_installer/ModuleInstallerBackend.java",
+  ]
+}
+
+static_library("module_installer") {
+  sources = [
+    "module_installer_backend.cc",
+  ]
+  deps = [
+    ":module_installer_jni_headers",
+    "//base",
+  ]
+}
+
 android_library("module_installer_test_java") {
   testonly = true
   java_files = [ "javatests/src/org/chromium/components/module_installer/ModuleInstallerRule.java" ]

components/module_installer/android/DEPS

 include_rules = [
+  "+base",
   "+components/crash/android",
 ]

components/module_installer/android/java/src-impl/org/chromium/components/module_installer/ModuleInstallerBackend.java

@@ -5,10 +5,13 @@
 package org.chromium.components.module_installer;
 
 import org.chromium.base.ThreadUtils;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.base.task.AsyncTask;
 
 import java.util.List;
 
 /** A backend for installing dynamic feature modules that contain the actual install logic. */
+@JNINamespace("module_installer")
 /* package */ abstract class ModuleInstallerBackend {
     private final OnFinishedListener mListener;
 
@@ -48,6 +51,28 @@ import java.util.List;
 
     /** To be called when module install has finished. */
     protected void onFinished(boolean success, List<String> moduleNames) {
-        mListener.onFinished(success, moduleNames);
+        ThreadUtils.assertOnUiThread();
+
+        // Call native to perform additional tasks (e.g., load resources). These
+        // tasks can be blocking, and are done asynchronously (outside the UI
+        // thread). Once done, return to call |mListender.onFinished()| on the
+        // UI thread.
+        // TODO(crbug.com/987252): Add timing metrics.
+        new AsyncTask<Void>() {
+            @Override
+            protected Void doInBackground() {
+                for (String moduleName : moduleNames) {
+                    nativeOnInstallModule(success, moduleName);
+                }
+                return null;
+            }
+
+            @Override
+            protected void onPostExecute(Void result) {
+                mListener.onFinished(success, moduleNames);
+            }
+        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
     }
+
+    private static native void nativeOnInstallModule(boolean success, String moduleName);
 }

components/module_installer/android/module_installer_backend.cc

+// Copyright 2019 The Chromium 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 "base/android/jni_android.h"
+#include "components/module_installer/android/module_installer_jni_headers/ModuleInstallerBackend_jni.h"
+
+namespace module_installer {
+
+// Handles native specific initialization in after module is installed. This may
+// be blocking, so the call should be done asynchronously.
+void JNI_ModuleInstallerBackend_OnInstallModule(
+    JNIEnv* env,
+    jboolean j_success,
+    const base::android::JavaParamRef<jstring>& j_module_name) {
+  // TODO(crbug.com/927131): Add code to detect DevUI DFM installation, and load
+  // the associated resource PAK file. This will require the following:
+  //   bool success = j_success;
+  //   (Needs #include "base/android/jni_string.h").
+  //   std::string module_name(ConvertJavaStringToUTF8(j_module_name));
+
+  // TODO(crbug.com/986960): Specialize this function to perform resource
+  // loading only. Required parameters can be injected to support data-driven
+  // flow. This will require massive refactoring first, however.
+}
+
+}  // namespace module_installer