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

content/browser/frame_host/navigation_entry_impl.cc

Index: content/browser/frame_host/navigation_entry_impl.cc
diff --git a/content/browser/frame_host/navigation_entry_impl.cc b/content/browser/frame_host/navigation_entry_impl.cc
index b021d5eda18cea37a92d27924094752c5b77a5b7..d9d13d55634294dc8b98749a08cedf7161a70cf0 100644
--- a/content/browser/frame_host/navigation_entry_impl.cc
+++ b/content/browser/frame_host/navigation_entry_impl.cc
@@ -292,6 +292,12 @@ int NavigationEntryImpl::GetHttpStatusCode() const {
 void NavigationEntryImpl::SetRedirectChain(
     const std::vector<GURL>& redirect_chain) {
   redirect_chain_ = redirect_chain;
+
+  size_t total_size = 0;
+  for (size_t i = 0; i < redirect_chain_.size(); ++i) {
+    total_size += redirect_chain_[i].Bytesize();
+  }
+  UMA_HISTOGRAM_COUNTS("Navigation.RedirectChainSizeInBytes", total_size);
 }
 
 const std::vector<GURL>& NavigationEntryImpl::GetRedirectChain() const {