Add a histogram for size of the memory used by redirect chain.

url/gurl.cc

Index: url/gurl.cc
diff --git a/url/gurl.cc b/url/gurl.cc
index c79cdba1aa21902651a6868579a4be7e0f326753..93d14c3da8ce8abdd047c0a9a538028a8fb4dda0 100644
--- a/url/gurl.cc
+++ b/url/gurl.cc
@@ -526,6 +526,11 @@ void GURL::Swap(GURL* other) {
   inner_url_.swap(other->inner_url_);
 }
 
+size_t GURL::Bytesize() const {
+  return sizeof(*this) + spec_.size() +
+      (inner_url_ ? inner_url_->Bytesize() : 0);
+}
+
 std::ostream& operator<<(std::ostream& out, const GURL& url) {
   return out << url.possibly_invalid_spec();
 }