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

base/memory/shared_memory_win.cc

Index: base/memory/shared_memory_win.cc
diff --git a/base/memory/shared_memory_win.cc b/base/memory/shared_memory_win.cc
index 7e0cf0bf23e67f0d13d22e56e0924cecda7456ce..2b59fab6ef86bb062989e80b5ead9f39d958269d 100644
--- a/base/memory/shared_memory_win.cc
+++ b/base/memory/shared_memory_win.cc
@@ -100,6 +100,11 @@ size_t SharedMemory::GetHandleLimit() {
   return static_cast<size_t>(1 << 23);
 }
 
+SharedMemoryHandle SharedMemory::ShallowCopyHandle(
+    const SharedMemoryHandle& handle) {
+  return handle;
+}
+
 bool SharedMemory::CreateAndMapAnonymous(size_t size) {
   return CreateAnonymous(size) && Map(size);
 }