[NTP Snippets] Fetch/load snippets on startup, and pass them on NTP creation

chrome/browser/android/ntp_snippets_bridge.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_NTP_SNIPPETS_BRIDGE_H_
 #define CHROME_BROWSER_ANDROID_NTP_SNIPPETS_BRIDGE_H_
 
 #include <jni.h>
 
 #include "base/android/scoped_java_ref.h"
 #include "base/scoped_observer.h"
 #include "components/ntp_snippets/ntp_snippets_service.h"
 
 // The C++ counterpart to NTPSnippetsBridge.java. Enables Java code to access
 // the list of snippets to show on the NTP
 class NTPSnippetsBridge : public ntp_snippets::NTPSnippetsServiceObserver {
  public:
-  explicit NTPSnippetsBridge(JNIEnv* env,
-                             jobject j_profile,
-                             jobject j_observer);
+  NTPSnippetsBridge(JNIEnv* env,
+                    const base::android::JavaParamRef<jobject>& j_profile);
   void Destroy(JNIEnv* env, const base::android::JavaParamRef<jobject>& obj);
 
+  void SetObserver(JNIEnv* env,
+                   const base::android::JavaParamRef<jobject>& obj,
+                   const base::android::JavaParamRef<jobject>& j_observer);
+
   static bool Register(JNIEnv* env);
 
  private:
   ~NTPSnippetsBridge() override;
 
   // NTPSnippetsServiceObserver overrides
   void NTPSnippetsServiceLoaded(
       ntp_snippets::NTPSnippetsService* service) override;
   void NTPSnippetsServiceShutdown(
       ntp_snippets::NTPSnippetsService* service) override;
 
   ntp_snippets::NTPSnippetsService* ntp_snippets_service_;
 
   base::android::ScopedJavaGlobalRef<jobject> observer_;
   ScopedObserver<ntp_snippets::NTPSnippetsService,
                  ntp_snippets::NTPSnippetsServiceObserver>
       snippet_service_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(NTPSnippetsBridge);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_NTP_SNIPPETS_BRIDGE_H_