Mark all Tast and brower-sanity tests as experimental on new arc-r bot.

There's a few failing tests in both suites, so just mark the tests as
experimental for now while they're greened up to prevent alerting
sheriffs.

Bug: 1092973
Change-Id: I0e777044720790753056a8ba3b83ba1fe302af8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2343632
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Auto-Submit: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796180}

testing/buildbot/chrome.ci.json

@@ -1384,6 +1384,7 @@
         }
       },
       {
+        "experiment_percentage": 100,
         "merge": {
           "args": [],
           "script": "//testing/merge_scripts/standard_gtest_merge.py"
@@ -1407,6 +1408,7 @@
         }
       },
       {
+        "experiment_percentage": 100,
         "merge": {
           "args": [],
           "script": "//testing/merge_scripts/standard_gtest_merge.py"

testing/buildbot/chrome.json

@@ -754,6 +754,7 @@
         }
       },
       {
+        "experiment_percentage": 100,
         "merge": {
           "args": [],
           "script": "//testing/merge_scripts/standard_gtest_merge.py"
@@ -777,6 +778,7 @@
         }
       },
       {
+        "experiment_percentage": 100,
         "merge": {
           "args": [],
           "script": "//testing/merge_scripts/standard_gtest_merge.py"

testing/buildbot/test_suite_exceptions.pyl

@@ -676,6 +676,13 @@
       'mac-archive-rel',
     ],
   },
+  'chrome_all_tast_tests': {
+    'modifications': {
+      'chromeos-eve-arc-r-chrome': {
+        'experiment_percentage': 100,  # https://crbug.com/1092973
+      },
+    },
+  },
   'chrome_java_test_pagecontroller_tests': {
     'remove_from': [
       'android-pie-arm64-rel',  # https://crbug.com/924194
@@ -1134,6 +1141,13 @@
       },
     },
   },
+  'cros_browser_sanity_test': {
+    'modifications': {
+      'chromeos-eve-arc-r-chrome': {
+        'experiment_percentage': 100,  # https://crbug.com/1092973
+      },
+    },
+  },
   'dawn_end2end_tests': {
     'remove_from': [
       'Linux FYI Release (AMD R7 240)', # https://crbug.com/915430