Disabling memory.top_7_stress perf test on webview

TBR=nednguyen
BUG=621489

Review-Url: https://codereview.chromium.org/2084183003
Cr-Commit-Position: refs/heads/master@{#401241}

tools/perf/benchmarks/memory.py

@@ -23,7 +23,8 @@ def Name(cls):
 # Disable on reference due to crbug.com/539728
 # Disable on all Mac as it's also failing on 10.11 and retina.
 # crbug.com/555045
-@benchmark.Disabled('mac', 'reference')
+# Disabling on WebView due to crbug.com/621489
+@benchmark.Disabled('mac', 'android-webview', 'reference')
 class MemoryTop7Stress(perf_benchmark.PerfBenchmark):
   """Use (recorded) real world web sites and measure memory consumption."""
   test = memory.Memory