Fix tracing args not being propagated correctly.

Change-Id: Idf2fe1f593133c4ee2f105fb794afc6fa05bae0d
Reviewed-on: https://chromium-review.googlesource.com/592549Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Michael Case <mikecase@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490975}

testing/buildbot/chromium.android.fyi.json

@@ -24,22 +24,16 @@
   "Android Tests with Tracing": {
     "instrumentation_tests": [
       {
-        "args": [
-          "--trace-all"
-        ],
-        "test": "chrome_public_test_apk"
+        "test": "chrome_public_test_apk",
+        "trace_output": true
       },
       {
-        "args": [
-          "--trace-all"
-        ],
-        "test": "chrome_sync_shell_test_apk"
+        "test": "chrome_sync_shell_test_apk",
+        "trace_output": true
       },
       {
-        "args": [
-          "--trace-all"
-        ],
-        "test": "content_shell_test_apk"
+        "test": "content_shell_test_apk",
+        "trace_output": true
       }
     ]
   },