Adds a --deterministic-fetch flag to headless_shell

headless/public/util/testing/generic_url_request_mocks.cc

Index: headless/public/util/testing/generic_url_request_mocks.cc
diff --git a/headless/public/util/testing/generic_url_request_mocks.cc b/headless/public/util/testing/generic_url_request_mocks.cc
index 4060950e122d886af2c6710d5145a881271251bf..08ff33d4b07e9d7664e44c94c34cdc142419e5b2 100644
--- a/headless/public/util/testing/generic_url_request_mocks.cc
+++ b/headless/public/util/testing/generic_url_request_mocks.cc
@@ -19,16 +19,18 @@ MockGenericURLRequestJobDelegate::~MockGenericURLRequestJobDelegate() {}
 
 bool MockGenericURLRequestJobDelegate::BlockOrRewriteRequest(
     const GURL& url,
+    const std::string& method,
     const std::string& referrer,
     GenericURLRequestJob::RewriteCallback callback) {
   if (should_block_)
-    callback(GenericURLRequestJob::RewriteResult::kDeny, GURL());
+    callback(GenericURLRequestJob::RewriteResult::kDeny, GURL(), method);
   return should_block_;
 }
 
 const GenericURLRequestJob::HttpResponse*
 MockGenericURLRequestJobDelegate::MaybeMatchResource(
     const GURL& url,
+    const std::string& method,
     const net::HttpRequestHeaders& request_headers) {
   return nullptr;
 }