Fixes d8 on windows following.

Broke by https://codereview.chromium.org/740493002/

BUG=
NOTRY=true
NOTREECHECKS=true

Review URL: https://codereview.chromium.org/734853004

Cr-Commit-Position: refs/heads/master@{#25409}

src/d8.cc

@@ -40,6 +40,8 @@
 #include "src/d8.h"
 
 #include "include/libplatform/libplatform.h"
+#include "include/v8-platform.h"
+
 #ifndef V8_SHARED
 #include "src/api.h"
 #include "src/base/cpu.h"