Add a method BrokerDuplicateSharedMemoryHandle() to the sandbox.

content/public/common/sandbox_init.h

Index: content/public/common/sandbox_init.h
diff --git a/content/public/common/sandbox_init.h b/content/public/common/sandbox_init.h
index 6f4b19c9ea4aefc037a3821babbc9d48e4d6ca04..1a312339ee8e58013604c64283055cdcbe102edb 100644
--- a/content/public/common/sandbox_init.h
+++ b/content/public/common/sandbox_init.h
@@ -7,7 +7,9 @@
 
 #include "base/files/scoped_file.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/shared_memory.h"
 #include "base/process/process.h"
+#include "base/process/process_handle.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 
@@ -26,6 +28,17 @@ struct SandboxInterfaceInfo;
 namespace content {
 class SandboxedProcessLauncherDelegate;
 
+#if defined(OS_WIN) || defined(OS_MACOSX)
+// This function allows a sandboxed process to duplicate a SharedMemoryHandle
+// to itself or to another process. The duplicated SharedMemoryHandle has the
+// same access rights as the original. Returns true on success, false
+// otherwise.
+CONTENT_EXPORT bool BrokerDuplicateSharedMemoryHandle(
+    const base::SharedMemoryHandle& source_handle,
+    base::ProcessId target_process_id,
+    base::SharedMemoryHandle* target_handle);
+#endif  // defined(OS_WIN) || defined(OS_MACOSX)
+
 #if defined(OS_WIN)
 
 // Initialize the sandbox for renderer, gpu, utility, worker, nacl, and plugin