headless: Switch to multiprocess mode by default

headless/lib/headless_content_main_delegate.cc

Index: headless/lib/headless_content_main_delegate.cc
diff --git a/headless/lib/headless_content_main_delegate.cc b/headless/lib/headless_content_main_delegate.cc
index 245341fcb43362d8ea6fbc222e2311b8b94c8ea7..e7ea8d7690d760ae8e03fd87614e2a57a6064215 100644
--- a/headless/lib/headless_content_main_delegate.cc
+++ b/headless/lib/headless_content_main_delegate.cc
@@ -41,8 +41,8 @@ HeadlessContentMainDelegate::~HeadlessContentMainDelegate() {
 bool HeadlessContentMainDelegate::BasicStartupComplete(int* exit_code) {
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
 
-  command_line->AppendSwitch(switches::kNoSandbox);
-  command_line->AppendSwitch(switches::kSingleProcess);
+  if (browser_->options().single_process_mode)
+    command_line->AppendSwitch(switches::kSingleProcess);
 
   // The headless backend is automatically chosen for a headless build, but also
   // adding it here allows us to run in a non-headless build too.