Make the timing of ManifestUpgradeDetectorFetcher::Start() call less subtle

chrome/browser/android/webapk/manifest_upgrade_detector_fetcher.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_WEBAPK_MANIFEST_UPGRADE_DETECTOR_FETCHER_H_
 #define CHROME_BROWSER_ANDROID_WEBAPK_MANIFEST_UPGRADE_DETECTOR_FETCHER_H_
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_weak_ref.h"
 #include "base/macros.h"
@@ skipping 35 matching lines @@
              const base::android::JavaParamRef<jobject>& obj,
              const base::android::JavaParamRef<jobject>& java_web_contents);
 
   // Registers JNI hooks.
   static bool Register(JNIEnv* env);
 
  private:
   ~ManifestUpgradeDetectorFetcher() override;
 
   // content::WebContentsObserver:
-  void DidFinishLoad(content::RenderFrameHost* render_frame_host,
-                     const GURL& validated_url) override;
+  void DidStopLoading() override;
+
+  // Fetches the installable data.
+  void FetchInstallableData();
 
   // Called once the installable data has been fetched.
   void OnDidGetInstallableData(const InstallableData& installable_data);
 
   // Called with the computed Murmur2 hash for the app icon.
   void OnGotIconMurmur2Hash(const std::string& icon_murmur2_hash);
 
   void OnDataAvailable(const ShortcutInfo& info,
                        const std::string& icon_murmur2_hash,
                        const SkBitmap& icon);
 
   // Points to the Java object.
   base::android::ScopedJavaGlobalRef<jobject> java_ref_;
 
   // The detector will only fetch the URL within the scope of the WebAPK.
   const GURL scope_;
 
   // The WebAPK's Web Manifest URL that the detector is looking for.
   const GURL web_manifest_url_;
 
+  // The URL for which the installable data is being fetched / was last fetched.
+  GURL last_fetched_url_;
+
   // Downloads app icon and computes Murmur2 hash.
   std::unique_ptr<WebApkIconHasher> icon_hasher_;
 
   // Downloaded data for |web_manifest_url_|.
   ShortcutInfo info_;
   SkBitmap icon_;
 
   base::WeakPtrFactory<ManifestUpgradeDetectorFetcher> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ManifestUpgradeDetectorFetcher);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_WEBAPK_MANIFEST_UPGRADE_DETECTOR_FETCHER_H_