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

chrome/browser/extensions/api/tab_capture/offscreen_tab.cc

Index: chrome/browser/extensions/api/tab_capture/offscreen_tab.cc
diff --git a/chrome/browser/extensions/api/tab_capture/offscreen_tab.cc b/chrome/browser/extensions/api/tab_capture/offscreen_tab.cc
index ea9a049fe73590aa7afb1fe0f55bc490e7814d4c..2bbb363797d68db2f570257681d3cf42cc722eb6 100644
--- a/chrome/browser/extensions/api/tab_capture/offscreen_tab.cc
+++ b/chrome/browser/extensions/api/tab_capture/offscreen_tab.cc
@@ -12,6 +12,7 @@
 #include "chrome/browser/ui/web_contents_sizer.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_source.h"
 #include "extensions/browser/extension_host.h"
 #include "extensions/browser/process_manager.h"
 
@@ -181,6 +182,8 @@ void OffscreenTab::Start(const GURL& start_url,
   // Create the WebContents to contain the off-screen tab's page.
   offscreen_tab_web_contents_.reset(
       WebContents::Create(WebContents::CreateParams(profile_.get())));
+  WebContentsSource::CreateForWebContentsAndLocation(
+      offscreen_tab_web_contents_.get(), FROM_HERE);
   offscreen_tab_web_contents_->SetDelegate(this);
   WebContentsObserver::Observe(offscreen_tab_web_contents_.get());