commit afd3c658f932029bb4953b1e2498a500799c6d7f
author Rakina Zata Amni <rakina@chromium.org> Tue Nov 30 06:19:17 2021
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue Nov 30 06:19:17 2021
tree 2c8066ce9ea9c1c22cdda436c5d7457d04fdfaef
parent 17a2bdda153bb1b59548793137a4a1c98ae1e2af

Create initial NavigationEntry on FrameTree initialization

Introduces the initial NavigationEntry, created on FrameTree
initialization, which is not associated with any navigation. It will
be replaced or lose its initial-ness when the first navigation in the
main frame committed. With the initial NavigationEntry, we can always
guarantee that a NavigationEntry always exists, even when no navigation
has committed. This has many benefits, as outlined in the doc:
https://docs.google.com/document/d/1H81oAG13f21fUf-IGHH8AnjNVJFtaThowl5Ki9hWw5E/edit#heading=h.sbcge7snrbj3

This CL introduces a few changes of behavior:
- After initialization, a FrameTree/NavigationController will always
  have a NavigationEntry. This will be reflected in content/public
  functions such as GetLastCommittedEntry(), GetVisibleEntry(),
  GetActiveEntry(), GetEntryCount(), GetLastCommittedEntryIndex(),
  GetCurrentEntryIndex()
- Navigations that are previously ignored because there is no committed
  entry to attach to or clone are now no longer ignored, except for the
  synchronous about:blank commit for window.open().

What this CL does not change:
- This CL does not change the behavior of any navigation that wasn't
  previously ignored, including initial empty document replacements.
- Web-platform-exposed behaviors, including history.length which will
  still start at 0 instead of 1 on a tab that hasn't navigated at all.
- Behavior of WebView APIs. WebBackForwardList, which exposes the
  whole session history list, remove initial NavigationEntry.
  getOriginalURL() will continue to return null when there's no
  committed navigation.
- Similarly, behavior of WebLayer APIs will not change. The values
  returned by APIs such as GetNavigationListCurrentIndex() and
  GetNavigationListSize() will continue to be what they were before (-1
  and 0 respectively) even when the initial NavigationEntry exists,
  preserving their previous behaviors.

This CL corresponds to Step 1 of the implementation plan in this doc:
https://docs.google.com/document/d/1H81oAG13f21fUf-IGHH8AnjNVJFtaThowl5Ki9hWw5E/edit#heading=h.8n643ug2wk11

This CL also applies all the changes detailed in the audit doc, except
for most of the "remove nullcheck" changes:
https://docs.google.com/spreadsheets/d/1MJyLNd6T5b7QWCO-qsSdnzmyLhubCddns1Uu9X8mEIk/edit#gid=0

Bug: 524208, 1215096
Change-Id: I9dbc17feeb451ae32954a8544cc32bb39ec37150
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3237491
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Reviewed-by: Clark DuVall <cduvall@chromium.org>
Reviewed-by: Devlin Cronin <rdevlin.cronin@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Daniel Rubery <drubery@chromium.org>
Owners-Override: Charlie Reis <creis@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/main@{#946343}