First failure:
https://build.chromium.org/p/chromium.gpu.fyi/builders/Android%20Release%20%28Nexus%209%29/builds/831

Searching for native crashes in: /b/c/b/Android_Release__Nexus_9_/src/out/Release/full_log
Unknown Android release, consider --[no-]packed-relocation-adjustments options
Reading Android symbols from: /b/c/b/Android_Release__Nexus_9_/src
Searching for Chrome symbols from within: /b/c/b/Android_Release__Nexus_9_/src/out/Release/lib.unstripped:/b/c/b/Android_Release__Nexus_9_/src/out/Release/lib:/b/c/b/Android_Release__Nexus_9_/src/out/Release
Traceback (most recent call last):
  File "/b/c/b/Android_Release__Nexus_9_/src/third_party/android_platform/development/scripts/stack", line 245, in <module>
    sys.exit(main(sys.argv[1:]))
  File "/b/c/b/Android_Release__Nexus_9_/src/third_party/android_platform/development/scripts/stack", line 236, in main
    arch_defined)
  File "/b/c/b/Android_Release__Nexus_9_/src/third_party/android_platform/development/scripts/stack_core.py", line 167, in ConvertTrace
    results = pool.map(PreProcessLog(load_vaddrs), chunks)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 251, in map
    return self.map_async(func, iterable, chunksize).get()
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 558, in get
    raise self._value
TypeError: expected string or buffer
step returned non-zero exit code: 1

Pretty much certain it is https://codereview.chromium.org/2159963002. 
Michael I think we should probably revert your CL, unfortunately.