Add dvlog_always_on to enable DVLOG without DEBUG and DCHECK option

ppapi/cpp/logging.h

 // Copyright (c) 2012 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 PPAPI_CPP_LOGGING_H_
 #define PPAPI_CPP_LOGGING_H_
 
 /// @file
 /// This file defines two macro asserts.
 
 #include <cassert>
 
 /// This macro asserts that 'a' evaluates to true. In debug mode, this macro
 /// will crash the program if the assertion evaluates to false. It (typically)
 /// has no effect in release mode.
+#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
 #define PP_DCHECK(a) assert(a)
+#else  // !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
+#define PP_DCHECK(a)
+#endif  // !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
 
 /// This macro asserts false in debug builds. It's used in code paths that you
 /// don't expect to execute.
 ///
 /// <strong>Example:</strong>
 ///
 /// @code
 /// if (!pointer) {
 /// // Pointer wasn't valid! This shouldn't happen.
 /// PP_NOTREACHED();
 /// return;
 /// }
 /// // Do stuff to the pointer, since you know it's valid.
 /// pointer->DoSomething();
 /// @endcode
+#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
 #define PP_NOTREACHED() assert(false)
+#else  // !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
+#define PP_NOTREACHED()
+#endif  // !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
 
 #endif  // PPAPI_CPP_LOGGING_H_