chore: cherry-pick e4abe032f3ad from chromium

[ppontes]

Ensure that BrowserContext is not used after it has been freed

Previously, it was possible for the BrowserContext to be destroyed
before ReportAnchorElementMetricsOnClick attempted to access it.

The fix uses the fact that NavigationPredictor extends
WebContentsObserver and checks that web_contents is still alive
before dereferencing BrowserContext. WebContents will always
outlive BrowserContext.

R=​​lukasza@chromium.org, ryansturm@chromium.org

(cherry picked from commit 7313a810ae0b1361cbe8453bc5496654dee24c76)

(cherry picked from commit f782a440339fa19a44422ca5e7165cddd1cffcc9)

Bug: 1197904
Change-Id: Iee4f126e92670a84d57c7a4ec7d6f702fb975c7e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2821639
Reviewed-by: Ryan Sturm ryansturm@chromium.org
Reviewed-by: Łukasz Anforowicz lukasza@chromium.org
Commit-Queue: Łukasz Anforowicz lukasza@chromium.org
Cr-Original-Original-Commit-Position: refs/heads/master@{#872021}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2827043
Auto-Submit: Robert Ogden robertogden@chromium.org
Commit-Queue: Ryan Sturm ryansturm@chromium.org
Cr-Original-Commit-Position: refs/branch-heads/4472@{#77}
Cr-Original-Branched-From: 3d60439cfb36485e76a1c5bb7f513d3721b20da1-refs/heads/master@{#870763}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2830308
Reviewed-by: Tarun Bansal tbansal@chromium.org
Commit-Queue: Tarun Bansal tbansal@chromium.org
Commit-Queue: Robert Ogden robertogden@chromium.org
Cr-Commit-Position: refs/branch-heads/4430@{#1297}
Cr-Branched-From: e5ce7dc4f7518237b3d9bb93cccca35d25216cbe-refs/heads/master@{#857950}

Notes: Security: backported fix for CVE-2021-21226.

[release-clerk]

Release Notes Persisted

Security: backported fix for CVE-2021-21226.