Fix CrOS mixins

Fixes swarming-related mixins not working on CrOS builders due to
generate_buildbot_json.py using the wrong dictionary in one spot.

Also switches several CrOS builders to use mixins instead of hard-coded
swarming dimensions since it now works.

Bug: 1080809
Change-Id: Idcde77f97c16a9039d719efd7d2fc750dbede885
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2200079
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#768501}

testing/buildbot/generate_buildbot_json.py

@@ -601,8 +601,8 @@ class BBJSONGenerator(object):
     elif self.is_chromeos(tester_config) and tester_config.get('use_swarming',
                                                                True):
       # The presence of the "device_type" dimension indicates that the tests
-      # are targetting CrOS hardware and so need the special trigger script.
-      dimension_sets = tester_config['swarming']['dimension_sets']
+      # are targeting CrOS hardware and so need the special trigger script.
+      dimension_sets = test['swarming']['dimension_sets']
       if all('device_type' in ds for ds in dimension_sets):
         test['trigger_script'] = {
           'script': '//testing/trigger_scripts/chromeos_device_trigger.py',

testing/buildbot/mixins.pyl

@@ -179,6 +179,24 @@
       'service_account': 'chrome-tester@chops-service-accounts.iam.gserviceaccount.com',
     },
   },
+  'chromeos-amd64-generic': {
+    'swarming': {
+      'dimensions': {
+        'kvm': '1',
+        'os': 'Ubuntu-16.04',
+        'pool': 'chromium.tests.cros.vm.template',
+      },
+    },
+  },
+  'chromeos-kevin': {
+    'swarming': {
+      'dimensions': {
+        'os': 'ChromeOS',
+        'device_type': 'kevin',
+        'pool': 'chrome-cros-dut.template',
+      },
+    },
+  },
   # TODO(crbug.com/812428): Remove this mixin after all test pools have migrated
   # to using templates.
   'chromium-template-pool': {

testing/buildbot/waterfalls.pyl

@@ -832,23 +832,15 @@
           'chromiumos_preflight',
         ],
         'browser_config': 'cros-chrome',
+        'mixins': [
+          'chromeos-amd64-generic',
+        ],
         'os_type': 'chromeos',
         'test_suites': {
           'gpu_telemetry_tests': 'gpu_chromeos_telemetry_tests',
           'gtest_tests': 'chromeos_vm_gtests',
           'isolated_scripts': 'chromeos_isolated_scripts',
         },
-        # TODO(crbug.com/1080809): Move this to a mixin once mixins are no
-        # longer broken for CrOS builders.
-        'swarming': {
-          'dimension_sets': [
-            {
-              'kvm': '1',
-              'os': 'Ubuntu-16.04',
-              'pool': 'chromium.tests.cros.vm.template',
-            },
-          ],
-        },
       },
       'chromeos-arm-generic-dbg': {
         'additional_compile_targets': [
@@ -864,19 +856,9 @@
         'additional_compile_targets': [
           'chromiumos_preflight',
         ],
-        # TODO(crbug.com/1080809): Move this to a mixin once mixins are no
-        # longer broken for CrOS builders.
-        'swarming': {
-          'dimension_sets': [
-            {
-              'os': 'ChromeOS',
-              'device_type': 'kevin',
-              # Special pool is needed for the devices since they also run
-              # swarmbucket builds.
-              'pool': 'chrome-cros-dut.template',
-            },
-          ],
-        },
+        'mixins': [
+          'chromeos-kevin',
+        ],
         'test_suites': {
           'gtest_tests': 'chromeos_device_gtests',
           'isolated_scripts': 'chromeos_remote_device_isolated_tests',
@@ -3136,20 +3118,12 @@
         'browser_config': 'cros-chrome',
         'os_type': 'chromeos',
         'skip_merge_script': True,
+        'mixins': [
+          'chromeos-amd64-generic',
+        ],
         'test_suites': {
           'gpu_telemetry_tests': 'gpu_noop_sleep_telemetry_test',
         },
-        # TODO(crbug.com/1080809): Move this to a mixin once mixins are no
-        # longer broken for CrOS builders.
-        'swarming': {
-          'dimension_sets': [
-            {
-              'kvm': '1',
-              'os': 'Ubuntu-16.04',
-              'pool': 'chromium.tests.cros.vm.template',
-            },
-          ],
-        },
       },
       'ChromeOS FYI Release (kevin)': {
         'additional_compile_targets': [
@@ -3159,24 +3133,12 @@
         'os_type': 'chromeos',
         'skip_merge_script': True,
         'mixins': [
+          'chromeos-kevin',
           'limited_capacity_bot',
         ],
         'test_suites': {
           'gpu_telemetry_tests': 'gpu_noop_sleep_telemetry_test',
         },
-        # TODO(crbug.com/1080809): Move this to a mixin once mixins are no
-        # longer broken for CrOS builders.
-        'swarming': {
-          'dimension_sets': [
-            {
-              'os': 'ChromeOS',
-              'device_type': 'kevin',
-              # Special pool is needed for the devices since they also run
-              # swarmbucket builds.
-              'pool': 'chrome-cros-dut.template',
-            },
-          ],
-        },
       },
       'GPU FYI Fuchsia Builder' : {
         'additional_compile_targets': [