Refactor UniqueNameHelper to use an adapter pattern for code sharing.

content/renderer/unique_name_helper.h

-// Copyright 2017 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 CONTENT_RENDERER_UNIQUE_NAME_HELPER_H_
-#define CONTENT_RENDERER_UNIQUE_NAME_HELPER_H_
-
-#include <string>
-
-#include "base/macros.h"
-
-namespace blink {
-class WebFrame;
-class WebLocalFrame;
-}  // namespace blink
-
-namespace content {
-
-class RenderFrameImpl;
-
-// Frame helper that manages the details of generating a quasi-stable unique
-// name for the frame. The name is unique within a page, and is used for:
-// - matching up session history items with recreated frames
-// - layout test results
-//
-// Description of the current unique name format
-// ---------------------------------------------
-// Changing the format of unique name has a high cost, because it breaks
-// backwards compatibility of session history (which stores unique names
-// generated in the past on user's disk). The evolution of unique name in a
-// mostly backwards-compatible way has resulted in the rather baroque format...
-//
-// uniqueName ::= <nullForMainFrame> | <assignedName> | <generatedName>
-// Note: generatedName is used if assignedName is non-unique / conflicts with
-// other frame's unique name.
-//
-// assignedName ::= value of iframe's name attribute
-//                  or value assigned to window.name
-// Note: The name must be assigned *before* the first real commit: afterwards,
-// the unique name is immutable.
-//
-// generatedName ::= oldGeneratedName newUniqueSuffix?
-// Note: newUniqueSuffix is only present if oldGeneratedName is not unique.
-//
-// oldGeneratedName ::= "<!--framePath //" ancestorChain
-//                      "/<!--frame" childCount "-->-->"
-// Note: oldGeneratedName is generated by the internal GenerateCandidate()
-// method.
-//
-// childCount ::= current number of siblings
-//
-// ancestorChain ::= concatenated unique names of ancestor chain,
-//                   terminated on the first ancestor (if any) starting with
-//                   "<!--framePath"; each ancestor's unique name is
-//                   separated by "/" character
-// Note: Two examples are provided below, with each portion of the name from a
-// distinct ancestor annotated.
-//
-// Example ancestor chain #1:
-//     "grandparent/parent"
-//     |    #1     |  #2  |
-// Example ancestor chain #2:
-//     "<!--framePath //foo/bar/<!--frame42-->-->/blah/foobar"
-//     |                    #1                   | #2 |  #3  |
-//
-// newUniqueSuffix ::= "<!--framePosition" framePosition "/" retryNumber "-->"
-//
-// framePosition ::= "-" numberOfSiblingsBeforeChild
-//                   [ framePosition-forParent? ]
-//
-// retryNumber ::= smallest non-negative integer resulting in unique name
-class UniqueNameHelper {
- public:
-  explicit UniqueNameHelper(RenderFrameImpl* render_frame);
-  ~UniqueNameHelper();
-
-  // Returns the generated unique name.
-  const std::string& value() const { return unique_name_; }
-
-  // Used to propagate an already calculated unique name.
-  //
-  // TODO(lukasza): It would be nice to assert uniqueness of the propagated
-  // name here but:
-  // 1) uniqueness is currently violated by provisional/old frame pairs.
-  // 2) there is an unresolved race between 2 OOPIFs, that can result in a
-  //    non-unique unique name: see https://crbug.com/558680#c14.
-  void set_propagated_name(const std::string& name) { unique_name_ = name; }
-
-  // Note: when creating a new child frame, the unique name needs to be
-  // calculated before the RenderFrameImpl is created. To avoid this chicken and
-  // egg problem, this method is static, which means that |parent| needs to be
-  // passed as a parameter.
-  static std::string GenerateNameForNewChildFrame(blink::WebFrame* parent,
-                                                  const std::string& name);
-
-  // Called after a browsing context name change to generate a new name. Note
-  // that this should not be called if the frame is no longer displaying the
-  // initial empty document, as unique name changes after that point will break
-  // history navigations. See https://crbug.com/607205.
-  void UpdateName(const std::string& name);
-
- private:
-  blink::WebLocalFrame* GetWebFrame() const;
-
-  RenderFrameImpl* const render_frame_;
-  std::string unique_name_;
-
-  DISALLOW_COPY_AND_ASSIGN(UniqueNameHelper);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_RENDERER_UNIQUE_NAME_HELPER_H_