Remove V8_WARN_UNUSED_RESULT for simple getters.

src/platform/mutex.h

Index: src/platform/mutex.h
diff --git a/src/platform/mutex.h b/src/platform/mutex.h
index ff519b9f0832fe24cdb1ae8e861f7203fd0be957..f08de4f3dcb31e318bf858d0a0546feb4fde574a 100644
--- a/src/platform/mutex.h
+++ b/src/platform/mutex.h
@@ -81,10 +81,10 @@ class Mutex V8_FINAL {
   typedef CRITICAL_SECTION NativeHandle;
 #endif
 
-  NativeHandle& native_handle() V8_WARN_UNUSED_RESULT {
+  NativeHandle& native_handle() {
     return native_handle_;
   }
-  const NativeHandle& native_handle() const V8_WARN_UNUSED_RESULT {
+  const NativeHandle& native_handle() const {
     return native_handle_;
   }
 
@@ -177,10 +177,10 @@ class RecursiveMutex V8_FINAL {
   // The implementation-defined native handle type.
   typedef Mutex::NativeHandle NativeHandle;
 
-  NativeHandle& native_handle() V8_WARN_UNUSED_RESULT {
+  NativeHandle& native_handle() {
     return native_handle_;
   }
-  const NativeHandle& native_handle() const V8_WARN_UNUSED_RESULT {
+  const NativeHandle& native_handle() const {
     return native_handle_;
   }