Enable cc_perftests on "Linux Perf (3)".

BUG=392620

Review URL: https://codereview.chromium.org/1003063003

Cr-Commit-Position: refs/heads/master@{#320688}

testing/buildbot/chromium.perf.json

 {
+  "Linux Perf (3)": {
+    "scripts": [
+      {
+        "name": "cc_perftests",
+        "script": "gtest_perf_test.py",
+        "args": ["cc_perftests", "--test-launcher-print-test-stdio=always"]
+      }
+    ]
+  },
   "Android Nexus4 Perf": {
     "scripts": [
       {