Fix OfflinePageDownloadBridge. Calls native->Java did not work due to missed JNI initialization.

chrome/browser/android/offline_pages/downloads/offline_page_download_bridge.cc

 // Copyright 2016 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 "chrome/browser/android/offline_pages/downloads/offline_page_download_bridge.h"
 
 #include <vector>
 
 #include "base/android/jni_string.h"
 #include "chrome/browser/android/offline_pages/offline_page_model_factory.h"
@@ skipping 37 matching lines @@
       ConvertUTF8ToJavaString(env, item.url.spec()).obj(),
       ConvertUTF8ToJavaString(env, item.target_path.value()).obj(),
       item.start_time.ToJavaTime(), item.total_bytes);
 }
 }  // namespace
 
 OfflinePageDownloadBridge::OfflinePageDownloadBridge(
     JNIEnv* env,
     const JavaParamRef<jobject>& obj,
     DownloadUIAdapter* download_ui_adapter)
-    : download_ui_adapter_(download_ui_adapter) {
+    : weak_java_ref_(env, obj),
+      download_ui_adapter_(download_ui_adapter) {
   DCHECK(download_ui_adapter_);
   download_ui_adapter_->AddObserver(this);
 }
 
 OfflinePageDownloadBridge::~OfflinePageDownloadBridge() {}
 
 // static
 bool OfflinePageDownloadBridge::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
@@ skipping 67 matching lines @@
 
   DownloadUIAdapter* adapter =
       DownloadUIAdapter::FromOfflinePageModel(offline_page_model);
 
   return reinterpret_cast<jlong>(
       new OfflinePageDownloadBridge(env, obj, adapter));
 }
 
 }  // namespace android
 }  // namespace offline_pages