Move unique name generation and tracking into //content.

third_party/WebKit/Source/core/page/FrameTree.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 30 matching lines @@
 const unsigned invalidChildCount = ~0U;
 
 }  // namespace
 
 FrameTree::FrameTree(Frame* thisFrame)
     : m_thisFrame(thisFrame), m_scopedChildCount(invalidChildCount) {}
 
 FrameTree::~FrameTree() {}
 
 void FrameTree::setName(const AtomicString& name) {
-  // This method should only be called for local frames
-  // (remote frames should be updated via setPrecalculatedName).
-  DCHECK(m_thisFrame->isLocalFrame());
-
-  // When this method is called, m_uniqueName should be already initialized.
-  // This assert helps ensure that early return (a few lines below) won't
-  // result in an uninitialized m_uniqueName.
-  DCHECK(!m_uniqueName.isNull() || (m_uniqueName.isNull() && !parent()));
-
-  // Do not recalculate m_uniqueName if there is no real change of m_name.
-  // This is not just a performance optimization - other code relies on the
-  // assumption that unique name shouldn't change if the assigned name didn't
-  // change (i.e. code in content::FrameTreeNode::SetFrameName).

[Charlie Reis, 2017/03/20 20:11:39]

Can you move a version of this comment to LocalDOMWindow::setName, if we're
still relying on it to be true?

[dcheng, 2017/03/21 22:03:42]

I've put a modified version of this comment in LocalDOMWindow::setName(). Though
I think the DCHECK in content::FrameTreeNode may be at least partly wrong: since
the name is calculated renderer-side, and my recollection is frame swap no
longer requires that the previous frame is synchronously unloaded, we could end
up in a situation where we get two DidChangeName IPCs requesting to change to
the same name, but with different unique names (for reasons)

-  if (m_name == name)
-    return;
-
   m_name = name;
-
-  // https://crbug.com/607205: Make sure m_uniqueName doesn't change after
-  // initial navigation - session history depends on this.
-  if (toLocalFrame(m_thisFrame)
-          ->loader()
-          .stateMachine()
-          ->committedFirstRealDocumentLoad())
-    return;
-
-  // Leave main frame's unique name set to a null string.
-  if (!parent())
-    return;
-
-  // Remove our old frame name so it's not considered in
-  // calculateUniqueNameForChildFrame call below.
-  m_uniqueName = AtomicString();
-
-  // Calculate a new unique name based on inputs.
-  setUniqueName(parent()->tree().calculateUniqueNameForChildFrame(
-      m_thisFrame, name, nullAtom));
-}
-
-void FrameTree::setPrecalculatedName(const AtomicString& name,
-                                     const AtomicString& uniqueName) {
-  m_name = name;
-
-  if (parent()) {
-    // Non-main frames should have a non-empty unique name.
-    DCHECK(!uniqueName.isEmpty());
-  } else {
-    // Unique name of main frames should always stay empty.
-    DCHECK(uniqueName.isEmpty());
-  }
-
-  // TODO(lukasza): We would like to assert uniqueness below (i.e. by calling
-  // setUniqueName), 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 |uniqueName| - see https://crbug.com/558680#c14.
-  m_uniqueName = uniqueName;
 }
 
 DISABLE_CFI_PERF
 Frame* FrameTree::parent() const {
   if (!m_thisFrame->client())
     return nullptr;
   return m_thisFrame->client()->parent();
 }
 
 Frame* FrameTree::top() const {
@@ skipping 11 matching lines @@
     return nullptr;
   return m_thisFrame->client()->nextSibling();
 }
 
 Frame* FrameTree::firstChild() const {
   if (!m_thisFrame->client())
     return nullptr;
   return m_thisFrame->client()->firstChild();
 }
 
-bool FrameTree::uniqueNameExists(const String& uniqueNameCandidate) const {
-  // This method is currently O(N), where N = number of frames in the tree.
-
-  // Before recalculating or checking unique name, we set m_uniqueName
-  // to an empty string (so the soon-to-be-removed name does not count
-  // as a collision).  This means that uniqueNameExists would return
-  // false positives when called with an empty |name|.
-  DCHECK(!uniqueNameCandidate.isEmpty());
-
-  for (Frame* frame = top(); frame; frame = frame->tree().traverseNext()) {
-    if (frame->tree().uniqueName() == uniqueNameCandidate)
-      return true;
-  }
-  return false;
-}
-
-AtomicString FrameTree::calculateUniqueNameForNewChildFrame(
-    const AtomicString& name,
-    const AtomicString& fallbackName) const {
-  AtomicString uniqueName =
-      calculateUniqueNameForChildFrame(nullptr, name, fallbackName);
-
-  // Caller will likely set the name via setPrecalculatedName, which
-  // unfortunately cannot currently assert uniqueness of the name - let's
-  // therefore assert the uniqueness here.
-  DCHECK(!uniqueNameExists(uniqueName));
-
-  return uniqueName;
-}
-
-String FrameTree::generateUniqueNameCandidate(bool existingChildFrame) const {
-  const char framePathPrefix[] = "<!--framePath ";
-  const int framePathPrefixLength = 14;
-  const int framePathSuffixLength = 3;
-
-  // Find the nearest parent that has a frame with a path in it.
-  HeapVector<Member<Frame>, 16> chain;
-  Frame* frame;
-  for (frame = m_thisFrame; frame; frame = frame->tree().parent()) {
-    if (frame->tree().uniqueName().startsWith(framePathPrefix))
-      break;
-    chain.push_back(frame);
-  }
-  StringBuilder uniqueName;
-  uniqueName.append(framePathPrefix);
-  if (frame) {
-    uniqueName.append(frame->tree().uniqueName().getString().substring(
-        framePathPrefixLength, frame->tree().uniqueName().length() -
-                                   framePathPrefixLength -
-                                   framePathSuffixLength));
-  }
-  for (int i = chain.size() - 1; i >= 0; --i) {
-    frame = chain[i];
-    uniqueName.append('/');
-    uniqueName.append(frame->tree().uniqueName());
-  }
-
-  uniqueName.append("/<!--frame");
-  uniqueName.appendNumber(childCount() - (existingChildFrame ? 1 : 0));
-  uniqueName.append("-->-->");
-
-  // NOTE: This name might not be unique - see http://crbug.com/588800.
-  return uniqueName.toAtomicString();
-}
-
-String FrameTree::generateFramePosition(Frame* child) const {
-  // This method is currently O(N), where N = number of frames in the tree.
-
-  StringBuilder framePositionBuilder;
-  framePositionBuilder.append("<!--framePosition");
-
-  if (!child) {
-    framePositionBuilder.append('-');
-    framePositionBuilder.appendNumber(childCount());
-    child = m_thisFrame;
-  }
-
-  while (child->tree().parent()) {
-    int numberOfSiblingsBeforeChild = 0;
-    Frame* sibling = child->tree().parent()->tree().firstChild();
-    while (sibling != child) {
-      sibling = sibling->tree().nextSibling();
-      numberOfSiblingsBeforeChild++;
-    }
-
-    framePositionBuilder.append('-');
-    framePositionBuilder.appendNumber(numberOfSiblingsBeforeChild);
-
-    child = child->tree().parent();
-  }
-
-  // NOTE: The generated string is not guaranteed to be unique, but should
-  // have a better chance of being unique than the string generated by
-  // generateUniqueNameCandidate, because we embed extra information into the
-  // string:
-  // 1) we walk the full chain of ancestors, all the way to the main frame
-  // 2) we use frame-position-within-parent (aka |numberOfSiblingsBeforeChild|)
-  //    instead of sibling-count.
-  return framePositionBuilder.toString();
-}
-
-AtomicString FrameTree::appendUniqueSuffix(
-    const String& prefix,
-    const String& likelyUniqueSuffix) const {
-  // Verify that we are not doing unnecessary work.
-  DCHECK(uniqueNameExists(prefix));
-
-  // We want unique name to be stable across page reloads - this is why
-  // we use a deterministic |numberOfTries| rather than a random number
-  // (a random number would be more likely to avoid a collision, but
-  // would change after every page reload).
-  int numberOfTries = 0;
-
-  // Keep trying |prefix| + |likelyUniqueSuffix| + |numberOfTries|
-  // concatenations until we get a truly unique name.
-  String candidate;
-  do {
-    StringBuilder uniqueNameBuilder;
-    uniqueNameBuilder.append(prefix);
-    uniqueNameBuilder.append(likelyUniqueSuffix);
-    uniqueNameBuilder.append('/');
-    uniqueNameBuilder.appendNumber(numberOfTries++);
-    uniqueNameBuilder.append("-->");
-
-    candidate = uniqueNameBuilder.toString();
-  } while (uniqueNameExists(candidate));
-  return AtomicString(candidate);
-}
-
-AtomicString FrameTree::calculateUniqueNameForChildFrame(
-    Frame* child,
-    const AtomicString& assignedName,
-    const AtomicString& fallbackName) const {
-  // Try to use |assignedName| (i.e. window.name or iframe.name) or
-  // |fallbackName| if possible.
-  const AtomicString& requestedName =
-      assignedName.isEmpty() ? fallbackName : assignedName;
-  if (!requestedName.isEmpty() && !uniqueNameExists(requestedName) &&
-      requestedName != "_blank")
-    return requestedName;
-
-  String candidate = generateUniqueNameCandidate(child);
-  if (!uniqueNameExists(candidate))
-    return AtomicString(candidate);
-
-  String likelyUniqueSuffix = generateFramePosition(child);
-  return appendUniqueSuffix(candidate, likelyUniqueSuffix);
-
-  // Description of the current unique name format
-  // ---------------------------------------------
-  //
-  // Changing the format of unique name is undesirable, because it breaks
-  // backcompatibility of session history (which stores unique names
-  // generated in the past on user's disk).  This incremental,
-  // backcompatibility-aware approach has resulted so far in the following
-  // rather baroque format... :
-  //
-  //   uniqueName ::= <nullForMainFrame> | <assignedName> | <generatedName>
-  //                 (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 (*before* the first
-  //                    real commit - afterwards unique name stays immutable).
-  //
-  //   generatedName ::= oldGeneratedName newUniqueSuffix?
-  //                  (newUniqueSuffix is only present if oldGeneratedName was
-  //                  not unique after all)
-  //
-  //   oldGeneratedName ::= "<!--framePath //" ancestorChain
-  //                        "/<!--frame" childCount "-->-->"
-  //                  (oldGeneratedName is generated by
-  //                  generateUniqueNameCandidate 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
-  //   ancestorChain example1: "grandparent/parent"
-  //  (ancestor's unique names :   #1--^   | #2-^ )
-  //   ancestorChain example2:
-  //                     "<!--framePath //foo/bar/<!--frame42-->-->/blah/foobar"
-  //  (ancestor's unique names:
-  //                              ^--#1--^                         | #2 | #3-^ )
-  //
-  //   newUniqueSuffix ::= "<!--framePosition" framePosition "/" retryNumber
-  //                       "-->"
-  //
-  //   framePosition ::= "-" numberOfSiblingsBeforeChild
-  //                     [ framePosition-forParent? ]
-  //
-  //   retryNumber ::= smallest non-negative integer resulting in unique name
-}
-
-void FrameTree::setUniqueName(const AtomicString& uniqueName) {
-  // Only subframes can have a non-null unique name - setUniqueName should
-  // only be called for subframes and never for a main frame.
-  DCHECK(parent());
-
-  DCHECK(!uniqueName.isEmpty() && !uniqueNameExists(uniqueName));
-  m_uniqueName = uniqueName;
-}
-
 Frame* FrameTree::scopedChild(unsigned index) const {
   unsigned scopedIndex = 0;
   for (Frame* child = firstChild(); child;
        child = child->tree().nextSibling()) {
     if (child->client()->inShadowTree())
       continue;
     if (scopedIndex == index)
       return child;
     scopedIndex++;
   }
@@ skipping 184 matching lines @@
 void showFrameTree(const blink::Frame* frame) {
   if (!frame) {
     printf("Null input frame\n");
     return;
   }
 
   printFrames(frame->tree().top(), frame, 0);
 }
 
 #endif