Add a method BrokerDuplicateSharedMemoryHandle() to the sandbox.

content/common/sandbox_linux/sandbox_init_linux.cc

Index: content/common/sandbox_linux/sandbox_init_linux.cc
diff --git a/content/common/sandbox_linux/sandbox_init_linux.cc b/content/common/sandbox_linux/sandbox_init_linux.cc
index 146b3528b697fbc29af225c0c596f6c8d2e94ea1..44ed36a2baaa3d4b5b906c591c7f9c5d880ab3da 100644
--- a/content/common/sandbox_linux/sandbox_init_linux.cc
+++ b/content/common/sandbox_linux/sandbox_init_linux.cc
@@ -23,4 +23,12 @@ scoped_ptr<sandbox::bpf_dsl::Policy> GetBPFSandboxBaselinePolicy() {
 }
 #endif  // !defined(OS_NACL_NONSFI)
 
+bool BrokerDuplicateSharedMemoryHandle(
+    base::SharedMemoryHandle source_handle,
+    base::ProcessId target_process_id,
+    base::SharedMemoryHandle* target_handle) {
+  *target_handle = base::SharedMemory::DeepCopyHandle(source_handle, true);
+  return base::SharedMemory::IsHandleValid(*target_handle);
+}
+
 }  // namespace content