Add WebView startup time benchmark

tools/perf/benchmarks/system_health.py

Index: tools/perf/benchmarks/system_health.py
diff --git a/tools/perf/benchmarks/system_health.py b/tools/perf/benchmarks/system_health.py
index 8037c349c72a354688d53825fff3b0c6ed999d76..cd462fa488982b815d68310cd918c1545e7af28e 100644
--- a/tools/perf/benchmarks/system_health.py
+++ b/tools/perf/benchmarks/system_health.py
@@ -46,6 +46,7 @@ class SystemHealthTop25(_SystemHealthBenchmark):
   def Name(cls):
     return 'system_health.top25'
 
+
 @benchmark.Disabled('android')  # crbug.com/601953
 @benchmark.Disabled('all')  # crbug.com/613050
 class SystemHealthKeyMobileSites(_SystemHealthBenchmark):
@@ -88,6 +89,26 @@ class _MemorySystemHealthBenchmark(perf_benchmark.PerfBenchmark):
     return not _IGNORED_STATS_RE.search(value.name)
 
 
+@benchmark.Enabled('android')

[Zhen Wang, 2016/06/08 22:29:56]

This enables this benchmark on all android bots. Do all android bots run webview
benchmarks or just Nexus 5X?

perezju, do you have any idea? Should we use
@benchmark.Enabled('android-webview')?

+class WebviewStartupSystemHealthBenchmark(_SystemHealthBenchmark):
+  """Benchmark that measures how long WebView takes to start up
+  and load a blank page.

[Zhen Wang, 2016/06/08 22:29:56]

This should be a 1-line description. And then put detailed description in a
separate paragraph.

+  """
+  page_set = page_sets.BlankPageSet
+
+  def CreateTimelineBasedMeasurementOptions(self):
+    options = timeline_based_measurement.Options()
+    options.SetTimelineBasedMetric('webviewStartupMetric')
+    options.config.enable_atrace_trace = True
+    options.config.enable_chrome_trace = False

[Zhen Wang, 2016/06/08 22:29:56]

Do we want to get atrace and chrome trace at the same time eventually? If so,
can you add a TODO here to indicate that?

[alexandermont, 2016/06/08 22:54:03]

Not in this benchmark. This benchmark just needs to know about the webview
startup time, which just requires atrace. If there were ever to be a metric that
required both atrace and chrome trace data, that would most likely be measured
by a different benchmark.

+    options.config.atrace_config.app_name = 'org.chromium.webview_shell'
+    return options
+
+  @classmethod
+  def Name(cls):
+    return 'system_health.webview_startup'
+
+
 class DesktopMemorySystemHealth(_MemorySystemHealthBenchmark):
   """Desktop Chrome Memory System Health Benchmark."""
   page_set = page_sets.DesktopMemorySystemHealthStorySet