Fix presubmit error.

src/data-flow.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 125 matching lines @@
 };
 
 
 // Simple fixed-capacity list-based worklist (managed as a queue) of
 // pointers to T.
 template<typename T>
 class WorkList BASE_EMBEDDED {
  public:
   // The worklist cannot grow bigger than size.  We keep one item empty to
   // distinguish between empty and full.
-  WorkList(int size)
+  explicit WorkList(int size)
       : capacity_(size + 1), head_(0), tail_(0), queue_(capacity_) {
     for (int i = 0; i < capacity_; i++) queue_.Add(NULL);
   }
 
   bool is_empty() { return head_ == tail_; }
 
   bool is_full() {
     // The worklist is full if head is at 0 and tail is at capacity - 1:
     //   head == 0 && tail == capacity-1 ==> tail - head == capacity - 1
     // or if tail is immediately to the left of head:
@@ skipping 501 matching lines @@
   List<BitVector*> variables_;
 
   DISALLOW_COPY_AND_ASSIGN(ReachingDefinitions);
 };
 
 
 } }  // namespace v8::internal
 
 
 #endif  // V8_DATAFLOW_H_