Upstream: Extract "WebAPK service" implementation from Chrome APK

chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java

Index: chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java
diff --git a/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java b/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java
index 9bc602db7669e8b66fb23266a35506ef75c806ff..6513050c52d7f1be52d5745053118c90ea2a41fe 100644
--- a/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java
+++ b/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java
@@ -5,18 +5,86 @@
 package org.chromium.webapk.shell_apk;
 
 import android.app.Service;
+import android.content.Context;
 import android.content.Intent;
 import android.os.IBinder;
+import android.util.Log;
 
-import org.chromium.webapk.lib.runtime_library.WebApkServiceImpl;
+import org.chromium.webapk.lib.common.WebApkUtils;
+
+import java.io.File;
+import java.lang.reflect.Constructor;
 
 /**
- * Implements services offered by the WebAPK to Chrome.
+ * Shell class for services provided by WebAPK to Chrome. Extracts code with implementation of
+ * services from .dex file in Chrome APK.
  */
 public class WebApkServiceFactory extends Service {
+    private static final String TAG = "cr_WebApkServiceFactory";
+
+    /**
+     * Name of the class with IBinder API implementation.
+     */
+    private static final String WEBAPK_SERVICE_IMPL_CLASS_NAME =
+            "org.chromium.webapk.lib.runtime_library.WebApkServiceImpl";
+
+    /*
+     * ClassLoader for loading {@link WEBAPK_SERVICE_IMPL_CLASS_NAME}. Static so that all
+     * {@link WebApkServiceFactory} service instatiations use the same ClassLoader during the app's
+     * lifetime.
+     */
+    private static ClassLoader sClassLoader;
 
     @Override
     public IBinder onBind(Intent intent) {
-        return new WebApkServiceImpl(this, R.drawable.app_icon);
+        ClassLoader webApkClassLoader = getClassLoaderInstance(this);
+        if (webApkClassLoader == null) {
+            Log.w(TAG, "Unable to create ClassLoader.");
+            return null;
+        }
+
+        try {
+            Class<?> webApkServiceImplClass =
+                    webApkClassLoader.loadClass(WEBAPK_SERVICE_IMPL_CLASS_NAME);
+            Constructor<?> webApkServiceImplConstructor =
+                    webApkServiceImplClass.getConstructor(Context.class, int.class);
+            return (IBinder) webApkServiceImplConstructor.newInstance(
+                    new Object[] {this, R.drawable.app_icon});
+        } catch (Exception e) {
+            Log.w(TAG, "Unable to create WebApkServiceImpl.");
+            e.printStackTrace();
+            return null;
+        }
+    }
+
+    /**
+     * Gets / creates ClassLaoder for loading {@link WEBAPK_SERVICE_IMPL_CLASS_NAME}.
+     * @param context WebAPK's context.
+     * @return The ClassLoader.
+     */
+    private static ClassLoader getClassLoaderInstance(Context context) {
+        if (sClassLoader == null) {
+            sClassLoader = createClassLoader(context);
+        }
+        return sClassLoader;
+    }
+
+    /**
+     * Creates ClassLoader for loading {@link WEBAPK_SERVICE_IMPL_CLASS_NAME}.
+     * @param context WebAPK's context.
+     * @return The ClassLoader.
+     */
+    private static ClassLoader createClassLoader(Context context) {
+        Context remoteContext = WebApkUtils.getHostBrowserContext(context);
+        if (remoteContext == null) {
+            Log.w(TAG, "Failed to get remote context.");
+            return null;
+        }
+
+        File localDexDir = context.getDir("dex", Context.MODE_PRIVATE);
+        File remoteDexFile =
+                new File(remoteContext.getDir("dex", Context.MODE_PRIVATE), "web_apk.dex");
+        return DexLoader.load(remoteContext, "web_apk.dex", WEBAPK_SERVICE_IMPL_CLASS_NAME,
+                remoteDexFile, localDexDir);
     }
 }