mus: Make --use-mus-in-renderer the default for --mash.

content/renderer/render_widget_unittest.cc

Index: content/renderer/render_widget_unittest.cc
diff --git a/content/renderer/render_widget_unittest.cc b/content/renderer/render_widget_unittest.cc
index 6d227f8bd7768aaef2d9bd8a646e8eb24bde34cb..2572bc2ae9e57847e0ad4bd13c74656aad0e5add 100644
--- a/content/renderer/render_widget_unittest.cc
+++ b/content/renderer/render_widget_unittest.cc
@@ -401,7 +401,7 @@ TEST_F(RenderWidgetUnittest, TouchDuringOrOutsideFlingUmaMetrics) {
 class PopupRenderWidget : public RenderWidget {
  public:
   explicit PopupRenderWidget(CompositorDependencies* compositor_deps)
-      : RenderWidget(1,
+      : RenderWidget(routing_id_++,
                      compositor_deps,
                      blink::WebPopupTypePage,
                      ScreenInfo(),
@@ -432,10 +432,13 @@ class PopupRenderWidget : public RenderWidget {
  private:
   IPC::TestSink sink_;
   MockWebWidget mock_webwidget_;
+  static int routing_id_;
 
   DISALLOW_COPY_AND_ASSIGN(PopupRenderWidget);
 };
 
+int PopupRenderWidget::routing_id_ = 1;
+
 class RenderWidgetPopupUnittest : public testing::Test {
  public:
   RenderWidgetPopupUnittest()