Revert of [NTP Snippets] Refresh the displayed snippets less frequently

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"
@@ skipping 23 matching lines @@
                           const JavaParamRef<jclass>& caller) {
   Profile* profile = ProfileManager::GetLastUsedProfile();
   NTPSnippetsServiceFactory::GetForProfile(profile)->FetchSnippets();
 }
 
 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();
+  // 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() {
-  if (observer_.is_null())
-    return;
+  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 : *ntp_snippets_service_) {
     titles.push_back(snippet.title());
     urls.push_back(snippet.url().spec());
     thumbnail_urls.push_back(snippet.salient_image_url().spec());
@@ skipping 12 matching lines @@
 
 void NTPSnippetsBridge::NTPSnippetsServiceShutdown() {
   observer_.Reset();
   snippet_service_observer_.Remove(ntp_snippets_service_);
 }
 
 // static
 bool NTPSnippetsBridge::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }