Use a fresh, temporary profile when running content_shell in DRT mode

content/shell/layout_test_controller_bindings.cc

Index: content/shell/layout_test_controller_bindings.cc
diff --git a/content/shell/layout_test_controller_bindings.cc b/content/shell/layout_test_controller_bindings.cc
index 59fecec607f6735946856f0ca923ee91e4f6b372..20131adc6e2d3763961e9b7c3da6e37811b15da1 100644
--- a/content/shell/layout_test_controller_bindings.cc
+++ b/content/shell/layout_test_controller_bindings.cc
@@ -124,6 +124,11 @@ LayoutTestControllerBindings::GetNativeFunction(v8::Handle<v8::String> name) {
     return v8::FunctionTemplate::New(SetDumpChildFramesAsText);
   if (name->Equals(v8::String::New("SetPrinting")))
     return v8::FunctionTemplate::New(SetPrinting);
+  if (name->Equals(v8::String::New(
+          "SetShouldStayOnPageAfterHandlingBeforeUnload"))) {
+    return v8::FunctionTemplate::New(
+        SetShouldStayOnPageAfterHandlingBeforeUnload);
+  }
   if (name->Equals(v8::String::New("SetWaitUntilDone")))
     return v8::FunctionTemplate::New(SetWaitUntilDone);