Allow the MITIGATION_WIN32K_DISABLE process mitigation to be set in the renderer sandbox.

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index a8474064ffe241a0b6fef7455c6fd2609e5bdb0f..c4a8a37b78f77e722020a2431a64da525b44cfde 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -430,6 +430,12 @@ const char kEnableDirectWrite[]             = "enable-direct-write";
 
 // Use high resolution timers for TimeTicks.
 const char kEnableHighResolutionTime[]      = "enable-high-resolution-time";
+
+// Enable the Win32K process mitigation policy for renderer processes which
+// prevents them from invoking user32 and gdi32 system calls which enter
+// the kernel. This is only supported on Windows 8 and beyond.
+const char kEnableWin32kRendererLockDown[]
+    = "enable_win32k_renderer_lockdown";
 #endif
 
 // Paint content on the compositor thread instead of the main thread.