Initialize a boolean in the ResourceResponse struct

Change-Id: I54c65ebbd2f252a8050503e809f835c3b23ec4d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1643472Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Yoav Weiss <yoavweiss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666179}

third_party/blink/renderer/platform/loader/fetch/resource_response.h

@@ -445,7 +445,7 @@ class PLATFORM_EXPORT ResourceResponse final {
 
   bool was_cached_ = false;
   bool connection_reused_ = false;
-  bool is_null_;
+  bool is_null_ = false;
   mutable bool have_parsed_age_header_ = false;
   mutable bool have_parsed_date_header_ = false;
   mutable bool have_parsed_expires_header_ = false;