Disable recording LSN UKM.

Change-Id: I1b0198675aa7ea3cf162001f5b57daa7997d194a
Bug: 1152552
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593867
Commit-Queue: Hongbo Song <hbsong@google.com>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837189}

chrome/browser/page_load_metrics/observers/core/ukm_page_load_metrics_observer.cc

@@ -56,7 +56,7 @@ namespace {
 
 const char kOfflinePreviewsMimeType[] = "multipart/related";
 extern const base::Feature kLayoutShiftNormalizationRecordUKM{
-    "LayoutShiftNormalizationRecordUKM", base::FEATURE_ENABLED_BY_DEFAULT};
+    "LayoutShiftNormalizationRecordUKM", base::FEATURE_DISABLED_BY_DEFAULT};
 
 bool IsSupportedProtocol(page_load_metrics::NetworkProtocol protocol) {
   switch (protocol) {