Reland "iOS: Save perf results under Documents/perf_result.json"

This will require a manual roll to downstream projects, since
the //test:perf_test target was introduced.

This is a reland of 10a8e7a9b5261a7e3ce19900ba3511be3b5911f8
Original change's description:
> iOS: Save perf results under Documents/perf_result.json
>
> TBR=henrika@webrtc.org
>
> Bug: webrtc:7156
> Change-Id: Ib00992cce0007e0b5c9274340df1a892f810b0c5
> Reviewed-on: https://webrtc-review.googlesource.com/29202
> Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
> Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
> Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#21244}

TBR=henrika@webrtc.org, phoglund@webrtc.org

No-Try: true
Bug: webrtc:7156
Change-Id: Iecdb108f605fd1c98acde4d50ab4f5a7b5f6bfaf
Reviewed-on: https://webrtc-review.googlesource.com/32761
Reviewed-by: Edward Lemur <ehmaldonado@webrtc.org>
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21252}
diff --git a/modules/remote_bitrate_estimator/BUILD.gn b/modules/remote_bitrate_estimator/BUILD.gn
index 2dc4b22..7c32ce1 100644
--- a/modules/remote_bitrate_estimator/BUILD.gn
+++ b/modules/remote_bitrate_estimator/BUILD.gn
@@ -146,6 +146,7 @@
       "../../rtc_base:rtc_numerics",
       "../../system_wrappers",
       "../../system_wrappers:field_trial_api",
+      "../../test:perf_test",
       "../../test:test_support",
       "../../voice_engine",
       "../bitrate_controller",