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

content/browser/frame_host/navigation_controller_impl.cc

Index: content/browser/frame_host/navigation_controller_impl.cc
diff --git a/content/browser/frame_host/navigation_controller_impl.cc b/content/browser/frame_host/navigation_controller_impl.cc
index 4fa5f0883f6b4e12bb3403cfdfdabe0ea4d04846..1c608f095837a9563877ca251cc25a6f2ace820b 100644
--- a/content/browser/frame_host/navigation_controller_impl.cc
+++ b/content/browser/frame_host/navigation_controller_impl.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"  // Temporary
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ -824,6 +825,14 @@ bool NavigationControllerImpl::RendererDidNavigate(
   active_entry->SetPageState(params.page_state);
   active_entry->SetRedirectChain(params.redirects);
 
+  // Use histogram to track memory impact of redirect chain because it's now
+  // not cleared for committed entries.
+  size_t redirect_chain_size = 0;
+  for (size_t i = 0; i < params.redirects.size(); ++i) {
+    redirect_chain_size += params.redirects[i].spec().length();
+  }
+  UMA_HISTOGRAM_COUNTS("Navigation.RedirectChainSize", redirect_chain_size);
+
   // Once it is committed, we no longer need to track several pieces of state on
   // the entry.
   active_entry->ResetForCommit();