Move unique name generation and tracking into //content.

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_