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

chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java b/chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java
index 022ec47182d32868246816a4dbc291e774f49966..936279dd595f5887c23ef20d07d17be46255304f 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java
@@ -511,13 +511,17 @@ public class ShortcutHelper {
     }
 
     /**
-     * Returns the URL with all but the last component of its path removed. This is used if the
-     * Web Manifest does not specify a scope. This method assumes that the URL passed in is a
-     * valid URL with a path that contains at least one "/".
+     * Generates a scope URL based on the passed in URL. It should be used if the Web Manifest
+     * does not specify a scope URL.
      * @param url The url to convert to a scope.
      * @return The scope.
      */
+    @CalledByNative
     public static String getScopeFromUrl(String url) {
+        // Scope URL is generated by:
+        // - Removing last component of the URL.
+        // - Clearing the URL's query and fragment.
+
         Uri uri = Uri.parse(url);
         List<String> path = uri.getPathSegments();
         int endIndex = path.size();
@@ -535,7 +539,6 @@ public class ShortcutHelper {
         }
         builder.path(scope_path);
 
-        // Clear out the query and fragment.
         builder.fragment("");
         builder.query("");
         return builder.build().toString();