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..abf75f65dc6e654a791d4e93f29ec712fece93ad 100644
--- a/content/public/browser/content_browser_client.cc
+++ b/content/public/browser/content_browser_client.cc
@@ -335,6 +335,11 @@ void ContentBrowserClient::OpenURL(
 const wchar_t* ContentBrowserClient::GetResourceDllName() {
   return nullptr;
 }
+
+base::string16 ContentBrowserClient::GetAppContainerSidForSandboxType(
+    int sandbox_type) const {
+  return base::string16();
+}
 #endif
 
 #if defined(VIDEO_HOLE)