Revert "[Perf Waterfall] Disable reference builds on Mac"

This reverts commit 0f4fde42.

Reason for revert: crbug.com/940075 is fixed now.

R=jbudorick@chromium.org

Original change's description:
> [Perf Waterfall] Disable reference builds on Mac
> 
> TBR=jbudorick@chromium.org
> 
> Bug: 940075
> Change-Id: Ibb863ac8c33d0f4057e0df78819893d8c0668d22
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1531106
> Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#642094}

TBR=crouleau@chromium.org,jbudorick@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 940075
Change-Id: I8ce4e3a6b867f6b8bf4d9dc0d4bc2c07e123c791
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1540311Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644596}

testing/buildbot/chromium.perf.json

@@ -1389,6 +1389,7 @@
           "-v",
           "--browser=release",
           "--upload-results",
+          "--run-ref-build",
           "--test-shard-map-filename=mac-10_12_laptop_low_end-perf_map.json",
           "--assert-gpu-compositing"
         ],
@@ -1618,6 +1619,7 @@
           "-v",
           "--browser=release",
           "--upload-results",
+          "--run-ref-build",
           "--test-shard-map-filename=mac-10_13_laptop_high_end-perf_map.json",
           "--assert-gpu-compositing"
         ],

tools/perf/core/perf_data_generator.py

@@ -429,9 +429,7 @@ NEW_PERF_RECIPE_MIGRATED_TESTERS = {
           'isolate': 'performance_test_suite',
           'num_shards': 26,
           'extra_args': [
-              # Temporarily disable reference builds on
-              # Mac to mitigate crbug.com/940075
-              #'--run-ref-build',
+              '--run-ref-build',
               ('--test-shard-map-filename='
                'mac-10_12_laptop_low_end-perf_map.json'),
               '--assert-gpu-compositing',
@@ -510,9 +508,7 @@ NEW_PERF_RECIPE_MIGRATED_TESTERS = {
         {
           'isolate': 'performance_test_suite',
           'extra_args': [
-            # Temporarily disable reference builds on
-            # Mac to mitigate crbug.com/940075
-            #'--run-ref-build',
+            '--run-ref-build',
             '--test-shard-map-filename=mac-10_13_laptop_high_end-perf_map.json',
               '--assert-gpu-compositing',
           ],