Add gtest_extras to hwasan-postsubmit

Test: Run tests under HWASan.
Bug: 193568145
Change-Id: Iff12a2dbbbb799463b43391e1bd554b33bb23f9e
diff --git a/TEST_MAPPING b/TEST_MAPPING
index c4002f2..90cb945 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -3,5 +3,10 @@
     {
       "name": "gtest_isolated_tests"
     }
+  ],
+  "hwasan-postsubmit": [
+    {
+      "name": "gtest_isolated_tests"
+    }
   ]
 }