Add methods to base::SharedMemory to replace common SharedMemoryHandle operations.

base/memory/shared_memory_posix.cc

Index: base/memory/shared_memory_posix.cc
diff --git a/base/memory/shared_memory_posix.cc b/base/memory/shared_memory_posix.cc
index ec4f01f35a3fdfa4132db9577fcc632ab306a406..904c95d6dddb801bf66aa67dc0bf724953e79987 100644
--- a/base/memory/shared_memory_posix.cc
+++ b/base/memory/shared_memory_posix.cc
@@ -176,6 +176,24 @@ size_t SharedMemory::GetHandleLimit() {
   return base::GetMaxFds();
 }
 
+// static
+SharedMemoryHandle SharedMemory::ShallowCopyHandle(
+    const SharedMemoryHandle& handle) {
+  SharedMemoryHandle new_handle = handle;
+  new_handle.auto_close = false;
+  return new_handle;
+}
+
+// static
+SharedMemoryHandle SharedMemory::DeepCopyHandle(
+    const SharedMemoryHandle& handle,
+    bool clean_up_resources_on_destruction) {
+  int duped_handle = HANDLE_EINTR(dup(handle.fd));
+  if (duped_handle < 0)
+    return base::SharedMemory::NULLHandle();
+  return base::FileDescriptor(duped_handle, clean_up_resources_on_destruction);
+}
+
 bool SharedMemory::CreateAndMapAnonymous(size_t size) {
   return CreateAnonymous(size) && Map(size);
 }