Revert of Revert of Make SharedMemoryHandle a class on Mac.

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 b1f85da93356c895de4d03753ab83589f31d19da..f58116adf8267ac4cea86a3920ac8de2ccc3845a 100644
--- a/base/memory/shared_memory_win.cc
+++ b/base/memory/shared_memory_win.cc
@@ -44,7 +44,7 @@
       name_(name) {
 }
 
-SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only)
+SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
     : mapped_file_(handle),
       memory_(NULL),
       read_only_(read_only),
@@ -52,7 +52,7 @@
       mapped_size_(0) {
 }
 
-SharedMemory::SharedMemory(SharedMemoryHandle handle,
+SharedMemory::SharedMemory(const SharedMemoryHandle& handle,
                            bool read_only,
                            ProcessHandle process)
     : mapped_file_(NULL),