Bug 1059662 - Disallow OOP app to embed in-proc apps. r=fabrice

Some mochitest that use embed-apps in an oop context is disabled.

dom/html/nsGenericHTMLFrameElement.cpp

@@ -7,6 +7,7 @@
 
 #include "nsGenericHTMLFrameElement.h"
 
+#include "mozilla/dom/ContentChild.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/ErrorResult.h"
 #include "GeckoProfiler.h"
@@ -437,6 +438,11 @@ nsGenericHTMLFrameElement::GetAppManifestURL(nsAString& aOut)
     return NS_OK;
   }
 
+  if (XRE_GetProcessType() != GeckoProcessType_Default) {
+    NS_WARNING("Can't embed-apps. Embed-apps is restricted to in-proc apps, see bug 1059662");
+    return NS_OK;
+  }
+
   nsAutoString appManifestURL;
   nsAutoString widgetManifestURL;