Get rid of (nearly all) uses of base/compiler_specific.h in mojo/edk/{embedder,system}.

We have our own equivalents for ALIGNOF() and ALIGNAS(). Some of these
includes were stale anyway (from when OVERRIDE was a macro defined in
compiler_specific.h).

The one remaining include is for MSVC_SUPPRESS_WARNING().

R=kulakowski@chromium.org

Review URL: https://codereview.chromium.org/1206113002.
diff --git a/mojo/edk/embedder/platform_handle.cc b/mojo/edk/embedder/platform_handle.cc
index 4675714..04d4f08 100644
--- a/mojo/edk/embedder/platform_handle.cc
+++ b/mojo/edk/embedder/platform_handle.cc
@@ -13,7 +13,6 @@
 #error "Platform not yet supported."
 #endif
 
-#include "base/compiler_specific.h"
 #include "base/logging.h"
 
 namespace mojo {
diff --git a/mojo/edk/embedder/scoped_platform_handle.h b/mojo/edk/embedder/scoped_platform_handle.h
index 0ec99b8..aec4482 100644
--- a/mojo/edk/embedder/scoped_platform_handle.h
+++ b/mojo/edk/embedder/scoped_platform_handle.h
@@ -5,10 +5,10 @@
 #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"
+#include "mojo/public/c/system/macros.h"
 
 namespace mojo {
 namespace embedder {
@@ -39,7 +39,7 @@
     other.handle_ = temp;
   }
 
-  PlatformHandle release() WARN_UNUSED_RESULT {
+  PlatformHandle release() MOJO_WARN_UNUSED_RESULT {
     PlatformHandle rv = handle_;
     handle_ = PlatformHandle();
     return rv;