Roll src/third_party/perfetto 7e40936b1d81..42f548873cf8 (2 commits)

https://android.googlesource.com/platform/external/perfetto.git/+log/7e40936b1d81..42f548873cf8

git log 7e40936b1d81..42f548873cf8 --date=short --first-parent --format='%ad %ae %s'
2020-03-27 treehugger-gerrit@google.com Merge "client API: Add missing PERFETTO_EXPORT definitions"
2020-03-27 treehugger-gerrit@google.com Merge "profilers: treat unset and =0 persist props the same"

Created with:
  gclient setdep -r src/third_party/perfetto@42f548873cf8

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

Bug: None
Tbr: perfetto-bugs@google.com
Change-Id: I24627c657f96315dd311bf12914fdefdbe676f58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124040Reviewed-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@{#754003}

DEPS

@@ -1228,7 +1228,7 @@ deps = {
   },
 
   'src/third_party/perfetto':
-    Var('android_git') + '/platform/external/perfetto.git' + '@' + '7e40936b1d81bf0ebea16c7f15e58fd3de88c8b6',
+    Var('android_git') + '/platform/external/perfetto.git' + '@' + '42f548873cf8580810748bd7b9cca178e524e600',
 
   'src/third_party/perl': {
       'url': Var('chromium_git') + '/chromium/deps/perl.git' + '@' + '6f3e5028eb65d0b4c5fdd792106ac4c84eee1eb3',