Fix presubmit error for recent revision.

R=fschneider@chromium.org

Review URL: http://codereview.chromium.org/8612003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10038 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/code-stubs.h

@@ -386,7 +386,7 @@ class FastCloneShallowObjectStub : public CodeStub {
   // 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);
   }