[tools/perf] Switch results.failures to results.had_failures

The results.failures property has been deprecated since the work to
remove FailureValue was completed.

Bug: 973837
Change-Id: I961e6e4c0b2f54b4c62f5ba4bd294fef9d44212e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1657903
Auto-Submit: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669067}

tools/perf/benchmarks/blink_perf_unittest.py

@@ -113,7 +113,7 @@ def testBlinkPerfTracingMetricsForMeasureAsync(self):
         ps=self._CreateStorySetForTestFile(
             'simple-blob-measure-async.html'),
         options=self._options)
-    self.assertFalse(results.failures)
+    self.assertFalse(results.had_failures)
     self.assertEquals(len(results.FindAllTraceValues()), 1)
 
     blob_requests = results.FindAllPageSpecificValuesNamed(
@@ -151,7 +151,7 @@ def testBlinkPerfLifecycleMethods(self):
         ps=self._CreateStorySetForTestFile(
             'lifecycle-methods.html'),
         options=self._options)
-    self.assertFalse(results.failures)
+    self.assertFalse(results.had_failures)
 
 
 # pylint: disable=protected-access