Adding method to create process using LowBox token in sandbox code.

sandbox/win/src/sandbox_policy_base.cc

Index: sandbox/win/src/sandbox_policy_base.cc
diff --git a/sandbox/win/src/sandbox_policy_base.cc b/sandbox/win/src/sandbox_policy_base.cc
index d3c920e6429c0e7119a34d423747ec921113603e..b8661921521eb6c40d6dc864328666fb3d5e0054 100644
--- a/sandbox/win/src/sandbox_policy_base.cc
+++ b/sandbox/win/src/sandbox_policy_base.cc
@@ -4,8 +4,6 @@
 
 #include "sandbox/win/src/sandbox_policy_base.h"
 
-#include <sddl.h>
-
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/logging.h"
@@ -310,13 +308,6 @@ ResultCode PolicyBase::SetAppContainer(const wchar_t* sid) {
   if (base::win::OSInfo::GetInstance()->version() < base::win::VERSION_WIN8)
     return SBOX_ALL_OK;
 
-  // Windows refuses to work with an impersonation token for a process inside
-  // an AppContainer. If the caller wants to use a more privileged initial
-  // token, or if the lockdown level will prevent the process from starting,
-  // we have to fail the operation.
-  if (lockdown_level_ < USER_LIMITED || lockdown_level_ != initial_level_)
-    return SBOX_ERROR_CANNOT_INIT_APPCONTAINER;
-
   DCHECK(!appcontainer_list_.get());
   appcontainer_list_.reset(new AppContainerAttributes);
   ResultCode rv = appcontainer_list_->SetAppContainer(sid, capabilities_);
@@ -477,13 +468,31 @@ ResultCode PolicyBase::MakeTokens(HANDLE* initial, HANDLE* lockdown) {
   }
 
   if (appcontainer_list_.get() && appcontainer_list_->HasAppContainer()) {
-    // Windows refuses to work with an impersonation token. See SetAppContainer
-    // implementation for more details.
-    if (lockdown_level_ < USER_LIMITED || lockdown_level_ != initial_level_)
-      return SBOX_ERROR_CANNOT_INIT_APPCONTAINER;
-
-    *initial = INVALID_HANDLE_VALUE;
-    return SBOX_ALL_OK;
+    NtCreateLowBoxToken CreateLowBox = NULL;
+    ResolveNTFunctionPtr("NtCreateLowBoxToken", &CreateLowBox);
+
+    HANDLE token_lowbox = NULL;
+    const SECURITY_CAPABILITIES& capabilities =
+        appcontainer_list_->GetCapabilities();
+
+    OBJECT_ATTRIBUTES obj_attr;
+    InitializeObjectAttributes(&obj_attr, NULL, 0, NULL, NULL);
+
+    NTSTATUS status = CreateLowBox(&token_lowbox,
+                                   *lockdown,
+                                   TOKEN_ALL_ACCESS,
+                                   &obj_attr,
+                                   capabilities.AppContainerSid,
+                                   capabilities.CapabilityCount,
+                                   capabilities.Capabilities,
+                                   0,
+                                   NULL);
+    if (!NT_SUCCESS(status)) {
+      return SBOX_ERROR_GENERIC;
+    }
+    DCHECK(token_lowbox);
+    ::CloseHandle(*lockdown);
+    *lockdown = token_lowbox;
   }
 
   // Create the 'better' token. We use this token as the one that the main