android: Run content_browsertests on Pie CQ at 50% experimentally.

On android CQ bots, content_browsertests currently only runs on L. But
due to test device shortage on L, it experiences high pending time quite
often.

Since we have got 290 more Pie test devices (crbug.com/1111436#c43),
content_browsertests should be able to run on Pie CQ.

But first, let's start with 50% to see how it goes.

Bug: 1111436
Change-Id: I7e5255c9a16bcc307a6f192e8d4d2f8076ad6f77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2534602Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Haiyang Pan <hypan@google.com>
Cr-Commit-Position: refs/heads/master@{#827071}

testing/buildbot/chromium.android.json

@@ -39144,6 +39144,55 @@
         "test": "chrome_java_test_webapk_launch_tests",
         "test_id_prefix": "ninja://chrome/test/android:chrome_java_test_webapk_launch_tests/"
       },
+      {
+        "args": [
+          "--gs-results-bucket=chromium-result-details",
+          "--recover-devices"
+        ],
+        "experiment_percentage": 50,
+        "merge": {
+          "args": [
+            "--bucket",
+            "chromium-result-details",
+            "--test-name",
+            "content_browsertests"
+          ],
+          "script": "//build/android/pylib/results/presentation/test_results_presentation.py"
+        },
+        "swarming": {
+          "can_use_on_swarming_builders": true,
+          "cipd_packages": [
+            {
+              "cipd_package": "infra/tools/luci/logdog/butler/${platform}",
+              "location": "bin",
+              "revision": "git_revision:ff387eadf445b24c935f1cf7d6ddd279f8a6b04c"
+            }
+          ],
+          "dimension_sets": [
+            {
+              "device_os": "PQ3A.190801.002",
+              "device_os_flavor": "google",
+              "device_os_type": "userdebug",
+              "device_type": "walleye",
+              "os": "Android"
+            }
+          ],
+          "output_links": [
+            {
+              "link": [
+                "https://luci-logdog.appspot.com/v/?s",
+                "=android%2Fswarming%2Flogcats%2F",
+                "${TASK_ID}%2F%2B%2Funified_logcats"
+              ],
+              "name": "shard #${SHARD_INDEX} logcats"
+            }
+          ],
+          "service_account": "chromium-tester@chops-service-accounts.iam.gserviceaccount.com",
+          "shards": 15
+        },
+        "test": "content_browsertests",
+        "test_id_prefix": "ninja://content/test:content_browsertests/"
+      },
       {
         "args": [
           "--gs-results-bucket=chromium-result-details",

testing/buildbot/test_suite_exceptions.pyl

@@ -1058,6 +1058,9 @@
           '--gtest_filter=-BackgroundTracingManagerBrowserTest.PerfettoSystemBackgroundScenario*',
         ],
       },
+      'android-pie-arm64-rel': {
+        'experiment_percentage': 50,
+      },
       'android-pie-x86-rel': {
         'args': [
           '--test-launcher-filter-file=../../testing/buildbot/filters/android.emulator_p.content_browsertests.filter',

testing/buildbot/test_suites.pyl

@@ -152,6 +152,11 @@
       'blink_platform_unittests': {},
       'chrome_java_test_pagecontroller_tests': {},
       'chrome_java_test_webapk_launch_tests': {},
+      'content_browsertests': {
+        'swarming': {
+          'shards': 15,
+        },
+      },
       'monochrome_public_bundle_fake_modules_smoke_test': {},
       'monochrome_public_bundle_smoke_test': {},
       'monochrome_public_smoke_test': {},