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

content/public/browser/web_contents.h

Index: content/public/browser/web_contents.h
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index c9fa8a011e04fed5db3aad0bb80354a194b29158..94ae46105bdd398034268f553c8e86a56a28b341 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -9,6 +9,7 @@
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
+#include "base/debug/stack_trace.h"
 #include "base/files/file_path.h"
 #include "base/process/kill.h"
 #include "base/strings/string16.h"
@@ -677,6 +678,9 @@ class WebContents : public PageNavigator,
   // as soon as they are ready.
   virtual void ResumeLoadingCreatedWebContents() = 0;
 
+  // Temporary to track down http://crbug.com/538612
+  virtual base::debug::StackTrace stack_trace() = 0;
+
 #if defined(OS_ANDROID)
   // Requests to resume the current media session.
   virtual void ResumeMediaSession() = 0;