Suppress console messages for all testharness tests.

third_party/WebKit/LayoutTests/resources/testharnessreport.js

 /*
  * THIS FILE INTENTIONALLY LEFT BLANK
  *
  * More specifically, this file is intended for vendors to implement
  * code needed to integrate testharness.js tests with their own test systems.
  *
  * Typically such integration will attach callbacks when each test is
  * has run, using add_result_callback(callback(test)), or when the whole test file has
  * completed, using add_completion_callback(callback(tests, harness_status)).
  *
  * For more documentation about the callback functions and the
  * parameters they are called with see testharness.js
  */
 
 (function() {
 
     var output_document = document;
 
     // Setup for WebKit JavaScript tests
     if (self.testRunner) {
         testRunner.dumpAsText();
         testRunner.waitUntilDone();
         testRunner.setCanOpenWindows();
         testRunner.setCloseRemainingWindowsWhenComplete(true);
         testRunner.setDumpJavaScriptDialogs(false);
+        testRunner.setDumpConsoleMessages(false);
     }
 
     // Disable the default output of testharness.js.  The default output formats
     // test results into an HTML table.  When that table is dumped as text, no
     // spacing between cells is preserved, and it is therefore not readable. By
     // setting output to false, the HTML table will not be created.
     // Also, disable timeout (except for explicit timeout), since the Blink
     // layout test runner has its own timeout mechanism.
     // See: https://github.com/w3c/testharness.js/blob/master/docs/api.md#setup
     setup({
@@ skipping 204 matching lines @@
             // another completion callback might generate more results.  So, we
             // don't dump the results immediately.
             setTimeout(done, 0);
         } else {
             // Parsing the test HTML isn't finished yet.
             window.addEventListener('load', done);
         }
     });
 
 })();