Add support for enabling DCHECKs in release mode

src/base/platform/mutex.h

 // Copyright 2013 the V8 project 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 V8_BASE_PLATFORM_MUTEX_H_
 #define V8_BASE_PLATFORM_MUTEX_H_
 
 #include "src/base/lazy-instance.h"
 #if V8_OS_WIN
 #include "src/base/win32-headers.h"
@@ skipping 50 matching lines @@
 
   NativeHandle& native_handle() {
     return native_handle_;
   }
   const NativeHandle& native_handle() const {
     return native_handle_;
   }
 
  private:
   NativeHandle native_handle_;
-#ifdef DEBUG
+#if DCHECK_IS_ON
   int level_;
 #endif
 
   V8_INLINE void AssertHeldAndUnmark() {
-#ifdef DEBUG
+#if DCHECK_IS_ON
     DCHECK_EQ(1, level_);
     level_--;
 #endif
   }
 
   V8_INLINE void AssertUnheldAndMark() {
-#ifdef DEBUG
+#if DCHECK_IS_ON
     DCHECK_EQ(0, level_);
     level_++;
 #endif
   }
 
   friend class ConditionVariable;
 
   DISALLOW_COPY_AND_ASSIGN(Mutex);
 };
 
@@ skipping 62 matching lines @@
 
   NativeHandle& native_handle() {
     return native_handle_;
   }
   const NativeHandle& native_handle() const {
     return native_handle_;
   }
 
  private:
   NativeHandle native_handle_;
-#ifdef DEBUG
+#if DCHECK_IS_ON
   int level_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(RecursiveMutex);
 };
 
 
 // POD RecursiveMutex initialized lazily (i.e. the first time Pointer() is
 // called).
 // Usage:
@@ skipping 29 matching lines @@
 
  private:
   Mutex* mutex_;
 
   DISALLOW_COPY_AND_ASSIGN(LockGuard);
 };
 
 } }  // namespace v8::base
 
 #endif  // V8_BASE_PLATFORM_MUTEX_H_