Make vector_as_array use std::vector::data and switch a few directories.

base/stl_util.h

Index: base/stl_util.h
diff --git a/base/stl_util.h b/base/stl_util.h
index e937d2f3ed9157d433cc62fb71958bd9c71cd6d9..3edcfe4cea0fe33dc76a1ed4d8f4cf18d2533584 100644
--- a/base/stl_util.h
+++ b/base/stl_util.h
@@ -98,17 +98,15 @@ STLCount(const Container& container, const T& val) {
   return std::count(container.begin(), container.end(), val);
 }
 
-// To treat a possibly-empty vector as an array, use these functions.
-// If you know the array will never be empty, you can use &*v.begin()
-// directly, but that is undefined behaviour if |v| is empty.
+// Deprecated: Use v.data() instead.
 template<typename T>
 inline T* vector_as_array(std::vector<T>* v) {
-  return v->empty() ? NULL : &*v->begin();
+  return v->data();
 }
 
 template<typename T>
 inline const T* vector_as_array(const std::vector<T>* v) {
-  return v->empty() ? NULL : &*v->begin();
+  return v->data();
 }
 
 // Return a mutable char* pointing to a string's internal buffer,