Fix Aura build break.

base/debug/trace_event.h

 // Copyright (c) 2011 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.
 
 // Trace events are for tracking application performance and resource usage.
 // Macros are provided to track:
 //    Begin and end of function calls
 //    Counters
 //
 // Events are issued against categories. Whereas LOG's
@@ skipping 621 matching lines @@
 
   Type type_;
   Value value_;
 };
 
 // TraceID encapsulates an ID that can either be an integer or pointer. Pointers
 // are mangled with the Process ID so that they are unlikely to collide when the
 // same pointer is used on different processes.
 class BASE_EXPORT TraceID {
  public:
-  TraceID() : data_(NULL) {}
+  TraceID() : data_(0u) {}
   TraceID(void* rhs);
   TraceID(unsigned long long rhs) : data_(static_cast<uint64>(rhs)) {}
   TraceID(unsigned long rhs) : data_(static_cast<uint64>(rhs)) {}
   TraceID(unsigned int rhs) : data_(static_cast<uint64>(rhs)) {}
   TraceID(long long rhs) : data_(static_cast<uint64>(rhs)) {}
   TraceID(long rhs) : data_(static_cast<uint64>(rhs)) {}
   TraceID(int rhs) : data_(static_cast<uint64>(rhs)) {}
 
   uint64 data() const { return data_; }
 
@@ skipping 321 matching lines @@
   Data* p_data_;
   Data data_;
 };
 
 }  // namespace internal
 
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_DEBUG_TRACE_EVENT_H_