perfetto: Build on Fuchsia

perfetto_unittests and content_unittests seem to be passing. Other test
suites (content_browsertests / services_unittests) aren't currently
supported on Fuchsia so can't yet verify that everything works in
practice.

Depends on aosp/853409 and aosp/859117.

Bug: 916074
Change-Id: I6d7c034fdf9e3086e08b6a1338e78f75a1c86afd
Reviewed-on: https://chromium-review.googlesource.com/c/1382134
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619606}

diff --git a/BUILD.gn b/BUILD.gn
index 0b73653..662dea5 100644
--- a/BUILD.gn
+++ b/BUILD.gn

@@ -664,7 +664,7 @@
     }
   }
 
-  if (is_mac || is_linux || is_android) {
+  if (is_mac || is_linux || is_android || is_fuchsia) {
     deps += [ "//third_party/perfetto:all" ]
   }