[test] Fix deterministic test shards.

tools/testrunner/objects/testcase.py

Index: tools/testrunner/objects/testcase.py
diff --git a/tools/testrunner/objects/testcase.py b/tools/testrunner/objects/testcase.py
index 7d8c21d2debc8a2e768310cac9e773a374391a52..113c624a35d66d43cdc88e49058c7af7b30bb5bd 100644
--- a/tools/testrunner/objects/testcase.py
+++ b/tools/testrunner/objects/testcase.py
@@ -100,3 +100,11 @@ class TestCase(object):
     send the name only and retrieve a process-local suite later.
     """
     return dict(self.__dict__, suite=self.suite.name)
+
+  def __cmp__(self, other):
+    # Make sure that test cases are sorted correctly if sorted without
+    # key function. But using a key function is preferred for speed.
+    return cmp(
+        (self.suite.name, self.path, self.flags),
+        (other.suite.name, other.path, other.flags),
+    )