[NTP Snippets] SnippetsBridge: register as SnippetsObserver only when we get a Java observer

chrome/browser/android/ntp/ntp_snippets_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/ntp/ntp_snippets_bridge.h"
 
 #include <jni.h>
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
 #include "chrome/browser/ntp_snippets/ntp_snippets_service_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_android.h"
 #include "components/ntp_snippets/ntp_snippet.h"
 #include "components/ntp_snippets/ntp_snippets_service.h"
 #include "jni/SnippetsBridge_jni.h"
 
 using base::android::ConvertJavaStringToUTF8;
 using base::android::JavaParamRef;
 using base::android::ToJavaArrayOfStrings;
 using base::android::ToJavaLongArray;
-using ntp_snippets::NTPSnippetsService;
-using ntp_snippets::NTPSnippetsServiceObserver;
 
 static jlong Init(JNIEnv* env,
                   const JavaParamRef<jobject>& obj,
                   const JavaParamRef<jobject>& j_profile) {
   NTPSnippetsBridge* snippets_bridge = new NTPSnippetsBridge(env, j_profile);
   return reinterpret_cast<intptr_t>(snippets_bridge);
 }
 
 NTPSnippetsBridge::NTPSnippetsBridge(JNIEnv* env,
                                      const JavaParamRef<jobject>& j_profile)
     : snippet_service_observer_(this) {
   Profile* profile = ProfileAndroid::FromProfileAndroid(j_profile);
   ntp_snippets_service_ = NTPSnippetsServiceFactory::GetForProfile(profile);
-  snippet_service_observer_.Add(ntp_snippets_service_);
 }
 
 void NTPSnippetsBridge::SetObserver(JNIEnv* env,
                                     const JavaParamRef<jobject>& obj,
                                     const JavaParamRef<jobject>& j_observer) {
   observer_.Reset(env, j_observer);
-  NTPSnippetsServiceLoaded(ntp_snippets_service_);
+  // This will call NTPSnippetsServiceLoaded.
+  snippet_service_observer_.Add(ntp_snippets_service_);
 }
 
 NTPSnippetsBridge::~NTPSnippetsBridge() {}
 
 void NTPSnippetsBridge::Destroy(JNIEnv* env, const JavaParamRef<jobject>& obj) {
   delete this;
 }
 
 void NTPSnippetsBridge::DiscardSnippet(JNIEnv* env,
                                        const JavaParamRef<jobject>& obj,
                                        const JavaParamRef<jstring>& url) {
   ntp_snippets_service_->DiscardSnippet(
       GURL(ConvertJavaStringToUTF8(env, url)));
 }
 
-void NTPSnippetsBridge::NTPSnippetsServiceLoaded(NTPSnippetsService* service) {
-  if (observer_.is_null())
-    return;
+void NTPSnippetsBridge::NTPSnippetsServiceLoaded() {
+  DCHECK(!observer_.is_null());
 
   std::vector<std::string> titles;
   std::vector<std::string> urls;
   std::vector<std::string> thumbnail_urls;
   std::vector<std::string> snippets;
   std::vector<int64_t> timestamps;
-  for (const ntp_snippets::NTPSnippet& snippet : *service) {
+  for (const ntp_snippets::NTPSnippet& snippet : *ntp_snippets_service_) {
     titles.push_back(snippet.title());
     urls.push_back(snippet.url().spec());
     thumbnail_urls.push_back(snippet.salient_image_url().spec());
     snippets.push_back(snippet.snippet());
     timestamps.push_back(snippet.publish_date().ToJavaTime());
   }
 
   JNIEnv* env = base::android::AttachCurrentThread();
   Java_SnippetsBridge_onSnippetsAvailable(
       env, observer_.obj(), ToJavaArrayOfStrings(env, titles).obj(),
       ToJavaArrayOfStrings(env, urls).obj(),
       ToJavaArrayOfStrings(env, thumbnail_urls).obj(),
       ToJavaArrayOfStrings(env, snippets).obj(),
       ToJavaLongArray(env, timestamps).obj());
 }
 
-void NTPSnippetsBridge::NTPSnippetsServiceShutdown(
-    NTPSnippetsService* service) {
+void NTPSnippetsBridge::NTPSnippetsServiceShutdown() {
   observer_.Reset();
   snippet_service_observer_.Remove(ntp_snippets_service_);
 }
 
 // static
 bool NTPSnippetsBridge::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }