[ Presubmit ] Add rule to prevent new tests from being added under runtime/observatory/tests/service

New service tests should be added to pkg/vm_service/test/ instead.

Change-Id: I22460753478c21956f56b5c7c29cb3dfbc500c21
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/350420
Reviewed-by: Jonas Termansen <sortie@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

PRESUBMIT.py

@@ -408,6 +408,26 @@ def _CheckCopyrightYear(input_api, output_api):
     ]
 
 
+def _CheckNoNewObservatoryServiceTests(input_api, output_api):
+    """Ensures that no new tests are added to the Observatory test suite."""
+    files = []
+
+    for f in input_api.AffectedFiles(include_deletes=False):
+        path = f.LocalPath()
+        if is_dart_file(path) and path.startswith(
+                "runtime/observatory/tests/service/") and f.Action(
+                ) == 'A' and os.path.isfile(path):
+            files.append(path)
+
+    if not files:
+        return []
+
+    return [
+        output_api.PresubmitError(
+            'New VM service tests should be added to pkg/vm_service/test, ' +
+            'not runtime/observatory/tests/service:\n' + '\n'.join(files))
+    ]
+
 def _CommonChecks(input_api, output_api):
     results = []
     results.extend(_CheckValidHostsInDEPS(input_api, output_api))
@@ -420,6 +440,7 @@ def _CommonChecks(input_api, output_api):
         input_api.canned_checks.CheckPatchFormatted(input_api, output_api))
     results.extend(_CheckCopyrightYear(input_api, output_api))
     results.extend(_CheckAnalyzerFiles(input_api, output_api))
+    results.extend(_CheckNoNewObservatoryServiceTests(input_api, output_api))
     return results