Merge V8 at r7668: Initial merge by Git.

Change-Id: I1703c8b4f5c63052451a22cf3fb878abc9a0ec75
diff --git a/src/jsregexp.h b/src/jsregexp.h
index 3ed5a7e..b9b2f60 100644
--- a/src/jsregexp.h
+++ b/src/jsregexp.h
@@ -1447,7 +1447,7 @@
 
 class OffsetsVector {
  public:
-  inline OffsetsVector(int num_registers)
+  explicit inline OffsetsVector(int num_registers)
       : offsets_vector_length_(num_registers) {
     if (offsets_vector_length_ > Isolate::kJSRegexpStaticOffsetsVectorSize) {
       vector_ = NewArray<int>(offsets_vector_length_);