Fix newly discovered presubmit errors.

src/splay-tree.h

 // Copyright 2010 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_SPLAY_TREE_H_
 #define V8_SPLAY_TREE_H_
 
 #include "src/allocation.h"
 
 namespace v8 {
@@ skipping 17 matching lines @@
 // template <typename Config, class Allocator = FreeStoreAllocationPolicy>
 //     class SplayTree;
 template <typename Config, class AllocationPolicy>
 class SplayTree {
  public:
   typedef typename Config::Key Key;
   typedef typename Config::Value Value;
 
   class Locator;
 
-  SplayTree(AllocationPolicy allocator = AllocationPolicy())
-      : root_(NULL), allocator_(allocator) { }
+  explicit SplayTree(AllocationPolicy allocator = AllocationPolicy())
+      : root_(NULL), allocator_(allocator) {}
   ~SplayTree();
 
   INLINE(void* operator new(size_t size,
                             AllocationPolicy allocator = AllocationPolicy())) {
     return allocator.New(static_cast<int>(size));
   }
   INLINE(void operator delete(void* p)) {
     AllocationPolicy::Delete(p);
   }
   // Please the MSVC compiler.  We should never have to execute this.
@@ skipping 144 matching lines @@
   Node* root_;
   AllocationPolicy allocator_;
 
   DISALLOW_COPY_AND_ASSIGN(SplayTree);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPLAY_TREE_H_