[blink_perf] Add log messages for tracing metrics in blink_perf

third_party/WebKit/PerformanceTests/resources/runner.js

 // There are tests for computeStatistics() located in LayoutTests/fast/harness/perftests
 
 if (window.testRunner) {
     testRunner.waitUntilDone();
     testRunner.dumpAsText();
 }
 
 (function () {
     var logLines = null;
     var completedIterations = -1;
@@ skipping 132 matching lines @@
         else if (doc.documentElement)
             doc.documentElement.offsetHeight;
     };
 
     function start(test, scheduler, runner) {
         if (!test) {
             PerfTestRunner.logFatalError("Got a bad test object.");
             return;
         }
         currentTest = test;
+
+        if (test.tracingCategories && !test.traceEventsToMeasure) {
+            PerfTestRunner.logFatalError("test's tracingCategories is " +
+                "specified but test's traceEventsToMeasure is empty");
+            return;
+        }
+
+        if (test.traceEventsToMeasure && !test.tracingCategories) {
+            PerfTestRunner.logFatalError("test's traceEventsToMeasure is " +
+                "specified but test's tracingCategories is empty");
+            return;
+        }
         iterationCount = test.iterationCount || (window.testRunner ? 5 : 20);
         if (test.warmUpCount && test.warmUpCount > 0)
             completedIterations = -test.warmUpCount;
         logLines = PerfTestRunner.bufferedLog || window.testRunner ? [] : null;
         PerfTestRunner.log("Running " + iterationCount + " times");
         if (test.doNotIgnoreInitialRun)
             completedIterations++;
 
         if (runner && test.tracingCategories && window.testRunner &&
             window.testRunner.supportTracing) {
             window.testRunner.traceEventsToMeasure = test.traceEventsToMeasure;
             window.testRunner.startTracing(test.tracingCategories, function() {
                 scheduleNextRun(scheduler, runner);
             });
         } else if (runner) {
+            if (test.tracingCategories && !(window.testRuner &&
+                  window.testRunner.supportTracing)) {
+                PerfTestRunner.log("Tracing based metrics are specified but " +
+                    "tracing is not supported on this platform. To get those " +
+                    "metrics from this test, you can run the test using " +
+                    "tools/perf/run_benchmarks script.");
+            }
             scheduleNextRun(scheduler, runner);
         }
     }
 
     function scheduleNextRun(scheduler, runner) {
         scheduler(function () {
             // This will be used by tools/perf/benchmarks/blink_perf.py to find
             // traces during the measured runs.
             if (completedIterations >= 0)
                 console.time("blink_perf");
@@ skipping 230 matching lines @@
 
             iframe.contentDocument.close();
             document.body.removeChild(iframe);
         };
 
         PerfTestRunner.measureTime(test);
     }
 
     window.PerfTestRunner = PerfTestRunner;
 })();