Implement GetSandboxType() on all platforms and implement for all process types.

content/public/browser/content_browser_client.cc

Index: content/public/browser/content_browser_client.cc
diff --git a/content/public/browser/content_browser_client.cc b/content/public/browser/content_browser_client.cc
index 0e07ec7c750374123038bdeb728a1a7620b32ec4..351b77cd25161d3f4b8471985c279ea19d0f7173 100644
--- a/content/public/browser/content_browser_client.cc
+++ b/content/public/browser/content_browser_client.cc
@@ -6,6 +6,7 @@
 
 #include "base/files/file_path.h"
 #include "content/public/browser/client_certificate_delegate.h"
+#include "content/public/common/sandbox_type.h"
 #include "ui/gfx/image/image_skia.h"
 #include "url/gurl.h"
 
@@ -335,6 +336,15 @@ void ContentBrowserClient::OpenURL(
 const wchar_t* ContentBrowserClient::GetResourceDllName() {
   return nullptr;
 }
+
+base::string16 ContentBrowserClient::GetAppContainerSidForSandboxType(
+    int sandbox_type) const {
+  // Embedders should override this method and return different SIDs for each
+  // sandbox type.

[nasko, 2015/06/24 13:11:38]

Let's put a Note: here to point out that content level tests will run all
process types in the same app container.

[Will Harris, 2015/06/24 15:17:20]

Done.

+  return base::string16(
+      L"S-1-15-2-3251537155-1984446955-2931258699-841473695-1938553385-"
+      L"924012148-129201922");
+}
 #endif
 
 #if defined(VIDEO_HOLE)