Isolate tests by running AtExit callbacks between them.

base/test/run_all_unittests.cc

Index: base/test/run_all_unittests.cc
diff --git a/base/test/run_all_unittests.cc b/base/test/run_all_unittests.cc
index 841b353262f1cc48df99dc70c419f9c10d2f4ad4..7b903586cb2214f26741c8ad85fccdbc093ab49e 100644
--- a/base/test/run_all_unittests.cc
+++ b/base/test/run_all_unittests.cc
@@ -5,5 +5,7 @@
 #include "base/test/test_suite.h"
 
 int main(int argc, char** argv) {
-  return TestSuite(argc, argv).Run();
+  TestSuite test_suite(argc, argv);
+  test_suite.EnforceTestIsolation();
+  return test_suite.Run();
 }