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

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 4546d52b7e3824a30aa9fc838f8434555224e975..6f2b8d1ef3c59b292bb58936cf586d38dd12368d 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1876,7 +1876,7 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     switches::kIpcDumpDirectory,
     switches::kIpcFuzzerTestcase,
 #endif
-    switches::kUseMusInRenderer,
+    switches::kNoUseMusInRenderer,

[jam, 2017/01/31 16:06:50]

nit: pattern here is to put switches not in ifdef sorted above, then end with
ifdefs. so move this up

[sadrul, 2017/01/31 17:01:04]

Done.

   };
   renderer_cmd->CopySwitchesFrom(browser_cmd, kSwitchNames,
                                  arraysize(kSwitchNames));