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This crash has been ongoing for a few years. The stack traces don't
lead to any obvious clues, and neither do the minidumps in Visual
Studio, since the most valuable local variable names have been
optimized away.

This CL adds two CHECKs and breaks apart two lines to try to get a
better clue as to why this crash is happening.

The crash seems to suggest we are using a dangling pointer.

Bug: 1024114
Change-Id: I085056561e776097120aab2ae075c32db49fcab7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2439485Reviewed-by: Orin Jaworski <orinj@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812210}