Fix presubmit error for recent revision.

src/code-stubs.h

 // Copyright 2011 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 368 matching lines @@
     return length_ * 4 +  mode_;
   }
 };
 
 
 class FastCloneShallowObjectStub : public CodeStub {
  public:
   // Maximum number of properties in copied object.
   static const int kMaximumClonedProperties = 6;
 
-  FastCloneShallowObjectStub(int length) : length_(length) {
+  explicit FastCloneShallowObjectStub(int length) : length_(length) {
     ASSERT_GE(length_, 0);
     ASSERT_LE(length_, kMaximumClonedProperties);
   }
 
   void Generate(MacroAssembler* masm);
 
  private:
   int length_;
 
   Major MajorKey() { return FastCloneShallowObject; }
@@ skipping 684 matching lines @@
   int MinorKey() { return 0; }
 
   void Generate(MacroAssembler* masm);
 
   DISALLOW_COPY_AND_ASSIGN(StoreArrayLiteralElementStub);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_CODE_STUBS_H_