[test-runner] Add dedicated test mode for tryserver.

BUG=

Review URL: https://codereview.chromium.org/1098883002

Cr-Commit-Position: refs/heads/master@{#27952}

tools/run-tests.py

@@ -112,8 +112,18 @@ MODES = {
     "execution_mode": "release",
     "output_folder": "release",
   },
-  # This mode requires v8 to be compiled with dchecks and slow dchecks.
+  # Normal trybot release configuration. There, dchecks are always on which
+  # implies debug is set. Hence, the status file needs to assume debug-like
+  # behavior/timeouts.
   "tryrelease": {
+    "flags": RELEASE_FLAGS,
+    "timeout_scalefactor": 1,
+    "status_mode": "debug",
+    "execution_mode": "release",
+    "output_folder": "release",
+  },
+  # This mode requires v8 to be compiled with dchecks and slow dchecks.
+  "slowrelease": {
     "flags": RELEASE_FLAGS + ["--enable-slow-asserts"],
     "timeout_scalefactor": 2,
     "status_mode": "debug",