tools/benchmarks: Fix failures in image decoding measurements.

tools/perf/benchmarks/image_decoding.py

Index: tools/perf/benchmarks/image_decoding.py
diff --git a/tools/perf/benchmarks/image_decoding.py b/tools/perf/benchmarks/image_decoding.py
index 7c897723d5281a0d9cd4429c381c413ad1afb0c2..68ed502664d72baca540836502d15ffbef424a9d 100644
--- a/tools/perf/benchmarks/image_decoding.py
+++ b/tools/perf/benchmarks/image_decoding.py
@@ -26,3 +26,11 @@ class ImageDecodingToughImageCases(perf_benchmark.PerfBenchmark):
 
   def GetExpectations(self):
     return page_sets.ImageDecodingMeasurementStoryExpectations()
+
+  def CustomizeBrowserOptions(self, options):
+    options.AppendExtraBrowserArgs([
+        # Disable asynchronous decodes in the renderer since these test
+        # rely on images have been decoded between consecutive
+        # requestAnimationFrames.
+        '--disable-checker-imaging'

[nednguyen, 2017/06/28 19:28:11]

Chris: I hope the overhauled version of image decode benchmark will not require
this flag? Otherwise, I worry that we may drift away from testing what we ship
to the users.

[Khushal, 2017/06/28 20:29:55]

If the only thing this benchmark wants to measure is the performance of the
decoding algorithm, then this flag should not have an impact. It only impacts
how these decodes are scheduled.

[cblume, 2017/06/28 21:15:28]

I think our concern is if the existing perf was thrown off, the new, overhauled
version will be thrown off as well.

And to add to the concern, I don't think the new version has a way to specify
flags like this.

It might force us to either 1.) find a better way to get the decoder time to the
page, or 2.) abandon this test (which has been a real consideration for a while
now)

+    ])