Add UMA metric to track usage of sending a mousedown to select elements.

third_party/WebKit/LayoutTests/resources/testharness.js

 /*global self*/
 /*jshint latedef: nofunc*/
 /*
 Distributed under both the W3C Test Suite License [1] and the W3C
 3-clause BSD License [2]. To contribute to a W3C Test Suite, see the
 policies and contribution forms [3].
 
 [1] http://www.w3.org/Consortium/Legal/2008/04-testsuite-license
 [2] http://www.w3.org/Consortium/Legal/2008/03-bsd-license
 [3] http://www.w3.org/2004/10/27-testcases
@@ skipping 505 matching lines @@
         var test_obj = new Test(test_name, properties);
         if (func) {
             test_obj.step(func, test_obj, test_obj);
         }
         return test_obj;
     }
 
     function promise_test(func, name, properties) {
         var test = async_test(name, properties);
         // If there is no promise tests queue make one.
-        test.step(function() {
-            if (!tests.promise_tests) {
-                tests.promise_tests = Promise.resolve();
-            }
-        });
+        if (!tests.promise_tests) {
+            tests.promise_tests = Promise.resolve();
+        }
         tests.promise_tests = tests.promise_tests.then(function() {
             return Promise.resolve(test.step(func, test, test))
                 .then(
                     function() {
                         test.done();
                     })
                 .catch(test.step_func(
                     function(value) {
                         if (value instanceof AssertionError) {
                             throw value;
@@ skipping 2134 matching lines @@
             tests.status.status = tests.status.ERROR;
             tests.status.message = e.message;
             tests.status.stack = e.stack;
         }
     });
 
     test_environment.on_tests_ready();
 
 })();
 // vim: set expandtab shiftwidth=4 tabstop=4: