Add a Physical Web JNI bridge to support native Physical Web clients

chrome/browser/android/physical_web/physical_web_data_source_android.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/physical_web/physical_web_data_source_android.h"
 
+#include <jni.h>
+
 #include "base/memory/ptr_util.h"
 #include "base/values.h"
+#include "chrome/browser/browser_process.h"
+#include "jni/UrlManager_jni.h"
+
+using base::android::AttachCurrentThread;
+using base::android::JavaParamRef;
+using base::android::ScopedJavaLocalRef;
 
 PhysicalWebDataSourceAndroid::PhysicalWebDataSourceAndroid() {
+  Initialize();
 }
 
-PhysicalWebDataSourceAndroid::~PhysicalWebDataSourceAndroid() {
+PhysicalWebDataSourceAndroid::~PhysicalWebDataSourceAndroid() {}
+
+void PhysicalWebDataSourceAndroid::Initialize() {
+  JNIEnv* env = AttachCurrentThread();
+
+  // Cache a reference to the singleton instance of UrlManager.
+  ScopedJavaLocalRef<jobject> url_manager = Java_UrlManager_getInstance(env);
+  url_manager_.Reset(env, env->NewGlobalRef(url_manager.obj()));
+  DCHECK(url_manager_.obj());

[gone, 2016/10/11 00:18:07]

Should be more straightforward; check:

AppBannerManagerAndroid::CreateJavaBannerManager() in C++ and
AppBannerManager.create() in Java

[mattreynolds, 2016/10/11 19:44:35]

I think you're suggesting we should be able to do initialization in one JNI call
(ie, without the native->Java call to get the UrlManager instance).  It's
possible but I couldn't find a way to do it cleanly.  For instance, the Init
method already receives a reference to the UrlManager, but to set the
url_manager_ member we'd need to cast the PhysicalWebDataSource* to a
PhysicalWebDataSourceAndroid* and add a public setter method.  It seems cleaner
to me to have PhysicalWebDataSourceAndroid make a second call to fetch the
UrlManager ref.

[gone, 2016/10/11 19:50:33]

Oh, I was actually referring to the thing you changed between patch sets; you
didn't need to make the local ref to make the global ref.  Sorry for being
unclear!

 }
 
 void PhysicalWebDataSourceAndroid::StartDiscovery(
     bool network_request_enabled) {
+  // On Android, scanning is started and stopped through the Java layer.
+  NOTREACHED();
 }
 
 void PhysicalWebDataSourceAndroid::StopDiscovery() {
+  // On Android, scanning is started and stopped through the Java layer.
+  NOTREACHED();
 }
 
 std::unique_ptr<base::ListValue> PhysicalWebDataSourceAndroid::GetMetadata() {
+  // TODO(mattreynolds): get the metadata from the Java layer
   return base::MakeUnique<base::ListValue>();
 }
 
 bool PhysicalWebDataSourceAndroid::HasUnresolvedDiscoveries() {
+  NOTIMPLEMENTED();
   return false;
 }
 
-void PhysicalWebDataSourceAndroid::RegisterListener(
-    PhysicalWebListener* listener) {
+// static
+bool PhysicalWebDataSourceAndroid::RegisterPhysicalWebDataSource(JNIEnv* env) {
+  return RegisterNativesImpl(env);
 }
 
-void PhysicalWebDataSourceAndroid::UnregisterListener(
-    PhysicalWebListener* listener) {
+static jlong Init(JNIEnv* env, const JavaParamRef<jobject>& obj) {
+  PhysicalWebDataSource* data_source =
+      g_browser_process->GetPhysicalWebDataSource();
+  return reinterpret_cast<intptr_t>(data_source);
 }