Use newer Chromium helper macro for defining move-only type.

mojo/edk/embedder/scoped_platform_handle.h

 // 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.
 
 #ifndef MOJO_EDK_EMBEDDER_SCOPED_PLATFORM_HANDLE_H_
 #define MOJO_EDK_EMBEDDER_SCOPED_PLATFORM_HANDLE_H_
 
 #include "base/compiler_specific.h"
 #include "base/move.h"
 #include "mojo/edk/embedder/platform_handle.h"
 #include "mojo/edk/system/system_impl_export.h"
 
 namespace mojo {
 namespace embedder {
 
 class MOJO_SYSTEM_IMPL_EXPORT ScopedPlatformHandle {
-  MOVE_ONLY_TYPE_FOR_CPP_03(ScopedPlatformHandle, RValue)
+  MOVE_ONLY_TYPE_WITH_MOVE_CONSTRUCTOR_FOR_CPP_03(ScopedPlatformHandle)
 
  public:
   ScopedPlatformHandle() {}
   explicit ScopedPlatformHandle(PlatformHandle handle) : handle_(handle) {}
   ~ScopedPlatformHandle() { handle_.CloseIfNecessary(); }
 
   // Move-only constructor and operator=.
-  ScopedPlatformHandle(RValue other) : handle_(other.object->release()) {}
-  ScopedPlatformHandle& operator=(RValue other) {
-    handle_ = other.object->release();
+  ScopedPlatformHandle(ScopedPlatformHandle&& other)
+      : handle_(other.release()) {}
+  ScopedPlatformHandle& operator=(ScopedPlatformHandle&& other) {
+    handle_ = other.release();

[jamesr, 2015/04/03 17:02:45]

this operator is incorrect, it doesn't handle self-assignment correctly

[mgraczyk, 2015/04/03 18:30:00]

Care to elaborate?

Here's how I see it. The requirement for self-assignment in a move assignment
operator is that it leave the operands on either side of the operator in a valid
state.  The state itself is unspecified.  It can be any valid state, but
generally we want self-assignment to be a noop.

If we write:

ScopedPlatformHandle(h) handle;
handle = std::move(handle);

What happens is

PlatformHandle rv = handle.handle_;
handle.handle_ = PlatformHandle();
handle.handle_ = rv;

which is a noop.

Is that not what you see?  I don't mind adding a check for self-assignment. 
It's more clear that it is correct in that case but I didn't want to change the
method body in this CL.

[jamesr, 2015/04/03 19:18:23]

Hmm, good point but I think having an idiomatically correct body would be much
clearer.  This works today because PlatformHandle is a simple data type but if
in the future it becomes something more complex in the future this body will
stop working as expected.

[mgraczyk, 2015/04/03 19:33:39]

I agree and added the check.

Although, too many "idioms" like this lead to code bloat from inlined move
constructors...

     return *this;
   }
 
   const PlatformHandle& get() const { return handle_; }
 
   void swap(ScopedPlatformHandle& other) {
     PlatformHandle temp = handle_;
     handle_ = other.handle_;
     other.handle_ = temp;
   }
@@ skipping 12 matching lines @@
   bool is_valid() const { return handle_.is_valid(); }
 
  private:
   PlatformHandle handle_;
 };
 
 }  // namespace embedder
 }  // namespace mojo
 
 #endif  // MOJO_EDK_EMBEDDER_SCOPED_PLATFORM_HANDLE_H_