Roll src/third_party/perfetto a0b94071e6bd..ac68e9c3dd09 (4 commits)

https://android.googlesource.com/platform/external/perfetto.git/+log/a0b94071e6bd..ac68e9c3dd09

git log a0b94071e6bd..ac68e9c3dd09 --date=short --no-merges --format='%ad %ae %s'
2019-09-09 lalitm@google.com trace_processor: migrate track table to new table macros
2019-09-09 lalitm@google.com trace_processor: make inserting into macro tables more explicit
2019-09-09 lalitm@google.com Merge "trace_processor: refactor Column to reduce boilerplate when adding types"
2019-09-09 hjd@google.com Merge "ui: Show full timestamp"

Created with:
  gclient setdep -r src/third_party/perfetto@ac68e9c3dd09

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/perfetto-chromium-autoroll
Please CC perfetto-bugs@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

TBR=perfetto-bugs@google.com

Bug: chromium:135177627,chromium:135177627
Change-Id: If7b064422fdcbcddc16a9798adbc047f3dc9274e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1792001Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#694839}

DEPS

@@ -1246,7 +1246,7 @@ deps = {
   },
 
   'src/third_party/perfetto':
-    Var('android_git') + '/platform/external/perfetto.git' + '@' + 'a0b94071e6bd0db3c4ab7740235b9103666a005d',
+    Var('android_git') + '/platform/external/perfetto.git' + '@' + 'ac68e9c3dd090d004ef03904b44dc69d2f63fa51',
 
   'src/third_party/perl': {
       'url': Var('chromium_git') + '/chromium/deps/perl.git' + '@' + '6f3e5028eb65d0b4c5fdd792106ac4c84eee1eb3',