This bug is similar to  issue #457656 .

Every day I build browser_tests_run from scratch and run isolate.py to get a local isolated build, for Linux and CrOS.

Every few days, the resulting browser_tests (and chrome itself) is crashy. The weird thing is, nuking my out directory and doing the same thing again seems to work, so this isn't deterministic behavior.

If my steps below are right, what's causing the bad builds?

Crash for commit ced319c78e3f9acc95394d81cc6763ed9a9e8371:

********** FULL OUTPUT BELOW **********

$ rm -rf out_linux/Release/*
$ GYP_DEFINES='test_isolation_mode=check use_goma=1' \
  GYP_GENERATOR_FLAGS='output_dir=out_linux' \
  bash -c 'gclient sync && ninja -C out_linux/Release -j 9999 -l 40 browser_tests_run'
$ ./tools/swarming_client/isolate.py remap -s out_linux/Release/browser_tests.isolated -o $snapshot_out_dir

$ $snapshot_out_dir//out_linux/Release/browser_tests --single_process
IMPORTANT DEBUGGING NOTE: each test is run inside its own process.
For debugging a test inside a debugger, use the
--gtest_filter=<your_test_name> flag along with either
--single_process (to run the test in one launcher/browser process) or
--single-process (to do the above, and also run Chrome in single-process mode).
Using sharding settings from environment. This is shard 0/1
Using 1 parallel jobs.
Note: Google Test filter = AppListStartPageWebUITest.Basic
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from AppListStartPageWebUITest, where TypeParam = 
[ RUN      ] AppListStartPageWebUITest.Basic
[133818:133818:0404/094055:WARNING:password_store_factory.cc(250)] Using basic (unencrypted) store for password storage. See https://chromium.googlesource.com/chromium/src/+/master/docs/linux_password_storage.md for more information about password storage
 options.
[133818:133818:0404/094055:WARNING:shell.cc(299)] Instance: exe:chrome attempting to register an instance for a process it created for target: exe:chrome_renderer without the mojo:shell{client_process} capability class.


#
# Fatal error in ../../v8/src/snapshot/snapshot.h, line 101
# Check failed: IsSane().
#

==== C stack trace ===============================

 1: 0x2c84db5
 2: 0x2a13dd8
 3: 0x2a13bb7
 4: 0x26a8b56
 5: 0x3a32b96
 6: 0x3895f4c
 7: 0x38963cd
 8: 0x389152a
 9: 0x2c8d577
10: 0x43c1df6
11: 0x43c0e9c
12: 0x43c0cfd
13: 0x43c09ca
14: 0x5a144b1
15: 0x4ba4fea
16: 0x4ba5e6a
17: 0x4ba4bd0
18: 0x4bbe0ba
19: 0x1107ec7
20: __libc_start_main
21: 0x58d329
Received signal 4 ILL_ILLOPN 000002c8622f
Received signal 11 SEGV_MAPERR 003000000020