ozone-linux: distinguish x11 and headless content_unittests.

This CL adds content_unittests for X11 with experimental
percentage set to 100% and different names for the one
running with headless and x11 backends.

Once we have weston in place, wayland will also be added.

Bug: 700309
Change-Id: I3ae0160028c4d94b8b81386240c824cf28483bb5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1781438
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693103}

testing/buildbot/chromium.linux.json

@@ -5790,6 +5790,27 @@
           "args": [],
           "script": "//testing/merge_scripts/standard_gtest_merge.py"
         },
+        "name": "headless_content_unittests",
+        "swarming": {
+          "can_use_on_swarming_builders": true,
+          "dimension_sets": [
+            {
+              "os": "Ubuntu-16.04"
+            }
+          ]
+        },
+        "test": "content_unittests"
+      },
+      {
+        "args": [
+          "--ozone-platform=x11"
+        ],
+        "experiment_percentage": 100,
+        "merge": {
+          "args": [],
+          "script": "//testing/merge_scripts/standard_gtest_merge.py"
+        },
+        "name": "x11_content_unittests",
         "swarming": {
           "can_use_on_swarming_builders": true,
           "dimension_sets": [

testing/buildbot/test_suites.pyl

@@ -4409,10 +4409,18 @@
       'services_unittests': {},
       'ozone_unittests': {},
       'ozone_x11_unittests': {},
-      'content_unittests': {
+      'headless_content_unittests': {
         'args': [
           '--ozone-platform=headless',
         ],
+        'test': 'content_unittests',
+      },
+      'x11_content_unittests': {
+        'experiment_percentage': 100,
+        'args': [
+          '--ozone-platform=x11',
+        ],
+        'test': 'content_unittests',
       },
     },