Update TabCapturePerformanceTest to more accurately time captures.

chrome/browser/extensions/api/tab_capture/tab_capture_performancetest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
 #include "base/strings/stringprintf.h"
 #include "base/test/trace_event_analyzer.h"
 #include "base/win/windows_version.h"
 #include "chrome/browser/extensions/extension_apitest.h"
@@ skipping 184 matching lines @@
 
     // The printed result will be the average time between frames in the
     // browser window.
     bool gpu_frames = PrintResults(
         analyzer.get(),
         test_name,
         "RenderWidget::didCommitAndDrawCompositorFrame",
         "ms");
     EXPECT_TRUE(gpu_frames);
 
-    // This prints out the average time between capture events.
-    // As the capture frame rate is capped at 30fps, this score
-    // cannot get any better than (lower) 33.33 ms.
+    // This prints out the average time between capture events. As the capture
+    // frame rate is capped at 30fps, this score cannot get any better than
+    // (lower) 33.33 ms. Note that we track the CaptureSucceeded event rather
+    // than Capture, as Capture only indicates that a capture was requested.
     EXPECT_TRUE(PrintResults(analyzer.get(),
                              test_name,
-                             "Capture",
+                             "CaptureSucceeded",

[hubbe, 2015/05/19 19:14:52]

How about printing out both results?
(Add a TODO to remove the "Capture" one in the future.)

[ericrk, 2015/05/19 20:02:08]

Good call - done.

                              "ms"));
   }
 };
 
 }  // namespace
 
 IN_PROC_BROWSER_TEST_P(TabCapturePerformanceTest, Performance) {
   RunTest("TabCapturePerformance");
 }
 
@@ skipping 26 matching lines @@
     TabCapturePerformanceTest,
     testing::Values(
         kScalingTestBase | kScaleQualityFast,
         kScalingTestBase | kScaleQualityGood,
         kScalingTestBase | kScaleQualityBest,
         kScalingTestBase | kScaleQualityFast | kSmallWindow,
         kScalingTestBase | kScaleQualityGood | kSmallWindow,
         kScalingTestBase | kScaleQualityBest | kSmallWindow));
 
 #endif  // USE_AURA