Change call-sites in trace viewer to use generators instead of iteration functions.

tracing/tracing/metrics/system_health/webview_startup_metric.html

Index: tracing/tracing/metrics/system_health/webview_startup_metric.html
diff --git a/tracing/tracing/metrics/system_health/webview_startup_metric.html b/tracing/tracing/metrics/system_health/webview_startup_metric.html
index b10c9f44638edd7900d472d70a48d1c059c62da6..10e873b97f5dc0a15c421c594c683274872faa93 100644
--- a/tracing/tracing/metrics/system_health/webview_startup_metric.html
+++ b/tracing/tracing/metrics/system_health/webview_startup_metric.html
@@ -15,7 +15,7 @@ found in the LICENSE file.
 
 tr.exportTo('tr.metrics.sh', function() {
   function webviewStartupMetric(values, model) {
-    model.iterateAllEvents(function(slice) {
+    for (var slice of model.getDescendantEvents()) {
       // WebViewStartupInterval is the title of the section of code that is
       // entered (via android.os.Trace.beginSection) when WebView is started
       // up. This value is defined in TelemetryActivity.java.
@@ -52,7 +52,7 @@ tr.exportTo('tr.metrics.sh', function() {
                 slice.cpuDuration),
             { description: 'WebView blank URL load CPU time' }));
       }
-    });
+    }
   };
 
   tr.metrics.MetricRegistry.register(webviewStartupMetric);