Make SingleThreadProxy a SchedulerClient

content/shell/renderer/test_runner/web_test_proxy.cc

Index: content/shell/renderer/test_runner/web_test_proxy.cc
diff --git a/content/shell/renderer/test_runner/web_test_proxy.cc b/content/shell/renderer/test_runner/web_test_proxy.cc
index d4524ee9ac1d2b4ffd1d000360a97677bf69ee18..4177b257610c8d0dd0673b64cd751cf891c477e0 100644
--- a/content/shell/renderer/test_runner/web_test_proxy.cc
+++ b/content/shell/renderer/test_runner/web_test_proxy.cc
@@ -7,9 +7,11 @@
 #include <cctype>
 
 #include "base/callback_helpers.h"
+#include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
+#include "content/public/common/content_switches.h"
 #include "content/shell/renderer/test_runner/TestInterfaces.h"
 #include "content/shell/renderer/test_runner/TestPlugin.h"
 #include "content/shell/renderer/test_runner/WebTestDelegate.h"
@@ -312,6 +314,10 @@ WebTestProxyBase::WebTestProxyBase()
       web_widget_(NULL),
       spellcheck_(new SpellCheckClient(this)),
       chooser_count_(0) {
+  // TODO(enne): using the scheduler introduces additional composite steps
+  // that create flakiness.  This should go away eventually.
+  base::CommandLine::ForCurrentProcess()->AppendSwitch(
+      switches::kDisableSingleThreadProxyScheduler);
   Reset();
 }