Track where WebContents are created in order to better understand issue.

chrome/browser/memory/tab_manager.cc

Index: chrome/browser/memory/tab_manager.cc
diff --git a/chrome/browser/memory/tab_manager.cc b/chrome/browser/memory/tab_manager.cc
index 55fde2097f6dd1372ba600689e0ddc302851f1f0..2a722639e6e1dbad4f316e4dd593fb82dc2f44e1 100644
--- a/chrome/browser/memory/tab_manager.cc
+++ b/chrome/browser/memory/tab_manager.cc
@@ -42,6 +42,7 @@
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_source.h"
 #include "content/public/common/page_importance_signals.h"
 
 #if defined(OS_CHROMEOS)
@@ -484,6 +485,7 @@ WebContents* TabManager::DiscardWebContentsAt(int index, TabStripModel* model) {
 
   WebContents* null_contents =
       WebContents::Create(WebContents::CreateParams(model->profile()));
+  WebContentsSource::CreateForWebContentsAndLocation(null_contents, FROM_HERE);
   // Copy over the state from the navigation controller to preserve the
   // back/forward history and to continue to display the correct title/favicon.
   null_contents->GetController().CopyStateFrom(old_contents->GetController());