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 601f9a26e313050b38226bd8f518e76c0846bdc6..3b159d142de117fa9ee11c42c45e8704c65ac55c 100644
--- a/content/browser/frame_host/navigation_controller_impl.cc
+++ b/content/browser/frame_host/navigation_controller_impl.cc
@@ -8,6 +8,7 @@
 #include "base/command_line.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"
@@ -826,6 +827,14 @@ 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();