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This CL adds a boolean to RenderFrameHost and NavigationHandle to check if they
are destroyed during a navigation commit, which would lead to a use-after-free
bug.

BUG=589365
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_site_isolation

Review URL: https://codereview.chromium.org/1759123002

Cr-Commit-Position: refs/heads/master@{#381713}