Revert a workaround commit for a UAF crash.

net/url_request/url_request_context.h

Index: net/url_request/url_request_context.h
diff --git a/net/url_request/url_request_context.h b/net/url_request/url_request_context.h
index ea555408415444d5480e5e51d1e926a1572fc298..53da67d7418b39e120bfd296b3fc5c6334d8ae1f 100644
--- a/net/url_request/url_request_context.h
+++ b/net/url_request/url_request_context.h
@@ -45,8 +45,7 @@ class URLRequestThrottlerManager;
 // these member variables, since they may be shared. For the ones that aren't
 // shared, URLRequestContextStorage can be helpful in defining their storage.
 class NET_EXPORT URLRequestContext
-    : NON_EXPORTED_BASE(public base::NonThreadSafe),
-      public base::SupportsWeakPtr<URLRequestContext> {
+    : NON_EXPORTED_BASE(public base::NonThreadSafe) {
  public:
   URLRequestContext();
   virtual ~URLRequestContext();