Expose v8dbg symbols so that V8's postmortem metadata is accessible in the...

Expose v8dbg symbols so that V8's postmortem metadata is accessible in the Chromium binary, if built

Exposing the v8dbg postmortem metadata symbols in Chromium builds (when
built, which they aren't by default) enables detailed analysis of V8 JS
execution by observing binary-level execution:
https://robert.ocallahan.org/2020/05/omniscient-js-debugging-in-pernosco.html

Bug: 1147409
Change-Id: I8f5863df2c2860ce3120c548e915f95bd16d321c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2528209Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827974}

AUTHORS

@@ -860,6 +860,7 @@ Robert Bear Travis <betravis@adobe.com>
 Robert Bradford <robert.bradford@intel.com>
 Robert Goldberg <goldberg@adobe.com>
 Robert Hogan <robhogan@gmail.com>
+Robert O'Callahan <rocallahan@gmail.com>
 Robert Nagy <robert.nagy@gmail.com>
 Robert Sesek <rsesek@bluestatic.org>
 Roger Zanoni <rogerzanoni@gmail.com>

build/linux/chrome.map

@@ -82,6 +82,8 @@ global:
   localtime64_r;
   localtime_r;
 
+  v8dbg_*;
+
 local:
   *;
 };