Adds sync brokering to Windows EDK

mojo/edk/embedder/platform_shared_buffer.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/embedder/platform_shared_buffer.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 235 matching lines @@
   base::SharedMemoryHandle handle(platform_handle.release().handle, false);
 #endif
 
   shared_memory_.reset(new base::SharedMemory(handle, read_only_));
   return true;
 }
 
 bool PlatformSharedBuffer::InitFromPlatformHandlePair(
     ScopedPlatformHandle rw_platform_handle,
     ScopedPlatformHandle ro_platform_handle) {
-#if defined(OS_WIN) || defined(OS_MACOSX)
+#if defined(OS_MACOSX)
   NOTREACHED();
   return false;
-#else
-  DCHECK(!shared_memory_);
+#else  // defined(OS_MACOSX)
 
+#if defined(OS_WIN)
+  base::SharedMemoryHandle handle(rw_platform_handle.release().handle,
+                                  base::GetCurrentProcId());
+  base::SharedMemoryHandle ro_handle(ro_platform_handle.release().handle,
+                                     base::GetCurrentProcId());
+#else  // defined(OS_WIN)
   base::SharedMemoryHandle handle(rw_platform_handle.release().handle, false);
-  shared_memory_.reset(new base::SharedMemory(handle, false));
-
   base::SharedMemoryHandle ro_handle(ro_platform_handle.release().handle,
                                      false);

[Will Harris, 2016/09/13 23:54:43]

I think this is correct...? as presumably you create the handle rw here then dup
it to a ro one on L274 but can you add a comment as it looks wonky to create a
ro_handle with |read_only| set to false.

Unless this is wrong, in which case why have the two stage create?

[Ken Rockot(use gerrit already), 2016/09/14 19:57:04]

The SharedMemoryHandle constructor doesn't know anything about read_only. The
|false| in these constructors is for |auto_close| (see base::FileDescriptor).
It's correct since we pass ownership of the handles into base::SharedMemory and
don't want them scoped to the local handle here.

[Will Harris, 2016/09/14 20:24:21]

Acknowledged.

+#endif  // defined(OS_WIN)
+
+  DCHECK(!shared_memory_);
+  shared_memory_.reset(new base::SharedMemory(handle, false));
   ro_shared_memory_.reset(new base::SharedMemory(ro_handle, true));
+  return true;
 
-  return true;
-#endif
+#endif  // defined(OS_MACOSX)
 }
 
 void PlatformSharedBuffer::InitFromSharedMemoryHandle(
     base::SharedMemoryHandle handle) {
   DCHECK(!shared_memory_);
 
   shared_memory_.reset(new base::SharedMemory(handle, read_only_));
 }
 
 PlatformSharedBufferMapping::~PlatformSharedBufferMapping() {
@@ skipping 28 matching lines @@
   base_ = static_cast<char*>(shared_memory_.memory()) + offset_rounding;
   return true;
 }
 
 void PlatformSharedBufferMapping::Unmap() {
   shared_memory_.Unmap();
 }
 
 }  // namespace edk
 }  // namespace mojo