Make WebAPK use "start URL longest path" as the scope if the scope is missing

chrome/browser/android/shortcut_helper.h

 // Copyright 2013 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_SHORTCUT_HELPER_H_
 #define CHROME_BROWSER_ANDROID_SHORTCUT_HELPER_H_
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_weak_ref.h"
 #include "base/callback_forward.h"
@@ skipping 92 matching lines @@
   // This method may generate an entirely new icon; if this is the case,
   // |is_generated| will be set to |true|.
   static SkBitmap FinalizeLauncherIcon(const SkBitmap& icon,
                                        const GURL& url,
                                        bool* is_generated);
 
   // Returns true if WebAPKs are enabled and there is a WebAPK installed which
   // can handle |url|.
   static bool IsWebApkInstalled(const GURL& url);
 
+  // Generates a scope URL based on the passed in |url|. It should be used
+  // when the Web Manifest does not specify a scope URL.
+  static GURL GetScopeFromURL(const GURL& url);
+
  private:
   ShortcutHelper() = delete;
   ~ShortcutHelper() = delete;
 
   DISALLOW_COPY_AND_ASSIGN(ShortcutHelper);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_SHORTCUT_HELPER_H_