Add chrome_junit_test shard experimental test suit.

This introduces an experimental test suite that shards junit tests
to run faster.

This is to land after junit sharding lands:
https://chromium-review.googlesource.com/c/chromium/src/+/2490847

Bug: 1138506
Change-Id: I01e38a2e80686383e48908110815551ac5526e72
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2493822
Commit-Queue: benjamin joyce <bjoyce@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Reviewed-by: Haiyang Pan <hypan@google.com>
Cr-Commit-Position: refs/heads/master@{#823770}

build/android/pylib/local/machine/local_machine_junit_test_run.py

@@ -228,8 +228,15 @@ def _GetTestClasses(file_path):
     # TODO(crbug.com/1144077): Use robolectric buildconfig file arg.
     if 'third_party/robolectric/' in test_jar:
       continue
-    test_classes += _GetTestClassesFromJar(
-        os.path.join(constants.DIR_SOURCE_ROOT, test_jar))
+
+    test_jar_path = os.path.join(constants.DIR_SOURCE_ROOT, test_jar)
+
+    # Bots write the classpath indexed from src.
+    if not os.path.exists(test_jar_path):
+      if test_jar.startswith('src' + os.path.sep):
+        test_jar_path = os.path.join(constants.DIR_SOURCE_ROOT, test_jar[4:])
+
+    test_classes += _GetTestClassesFromJar(test_jar_path)
 
   logging.info('Found %d test classes in class_path jars.', len(test_classes))
   return test_classes

testing/buildbot/chromium.android.json

@@ -1768,6 +1768,16 @@
         "test": "chrome_junit_tests",
         "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
       },
+      {
+        "args": [
+          "--shards=6"
+        ],
+        "experiment_percentage": 10,
+        "name": "chrome_junit_tests_with_shards",
+        "swarming": {},
+        "test": "chrome_junit_tests",
+        "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
+      },
       {
         "name": "components_junit_tests",
         "swarming": {},
@@ -20680,6 +20690,16 @@
         "test": "chrome_junit_tests",
         "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
       },
+      {
+        "args": [
+          "--shards=6"
+        ],
+        "experiment_percentage": 10,
+        "name": "chrome_junit_tests_with_shards",
+        "swarming": {},
+        "test": "chrome_junit_tests",
+        "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
+      },
       {
         "name": "components_junit_tests",
         "swarming": {},
@@ -29686,6 +29706,17 @@
         "test": "chrome_junit_tests",
         "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
       },
+      {
+        "args": [
+          "--shards=6"
+        ],
+        "experiment_percentage": 10,
+        "isolate_profile_data": true,
+        "name": "chrome_junit_tests_with_shards",
+        "swarming": {},
+        "test": "chrome_junit_tests",
+        "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
+      },
       {
         "isolate_profile_data": true,
         "name": "components_junit_tests",

testing/buildbot/chromium.clang.json

@@ -8316,6 +8316,16 @@
         "test": "chrome_junit_tests",
         "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
       },
+      {
+        "args": [
+          "--shards=6"
+        ],
+        "experiment_percentage": 10,
+        "name": "chrome_junit_tests_with_shards",
+        "swarming": {},
+        "test": "chrome_junit_tests",
+        "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
+      },
       {
         "name": "components_junit_tests",
         "swarming": {},

testing/buildbot/chromium.fyi.json

@@ -7183,6 +7183,17 @@
         "test": "chrome_junit_tests",
         "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
       },
+      {
+        "args": [
+          "--shards=6"
+        ],
+        "experiment_percentage": 10,
+        "isolate_profile_data": true,
+        "name": "chrome_junit_tests_with_shards",
+        "swarming": {},
+        "test": "chrome_junit_tests",
+        "test_id_prefix": "ninja://chrome/android:chrome_junit_tests/"
+      },
       {
         "isolate_profile_data": true,
         "name": "components_junit_tests",

testing/buildbot/test_suites.pyl

@@ -771,6 +771,13 @@
       'base_junit_tests': {},
       'chrome_java_test_pagecontroller_junit_tests': {},
       'chrome_junit_tests': {},
+      'chrome_junit_tests_with_shards': {
+        'args': [
+          '--shards=6',
+        ],
+        'test': 'chrome_junit_tests',
+        'experiment_percentage': 10,
+      },
       'components_junit_tests': {},
       'content_junit_tests': {},
       'device_junit_tests': {},