Apply test isolation goodness to net_unittests.

net/base/run_all_unittests.cc

Index: net/base/run_all_unittests.cc
diff --git a/net/base/run_all_unittests.cc b/net/base/run_all_unittests.cc
index 2bed0b7b55b53f2f32958074282a8ba393eae45f..178bd5b73838b6daee2902ef681b04880c4b7012 100644
--- a/net/base/run_all_unittests.cc
+++ b/net/base/run_all_unittests.cc
@@ -30,5 +30,7 @@
 #include "net/base/net_test_suite.h"
 
 int main(int argc, char** argv) {
-  return NetTestSuite(argc, argv).Run();
+  NetTestSuite test_suite(argc, argv);
+  test_suite.EnforceTestIsolation();
+  return test_suite.Run();
 }