Add metrics for style update time before FCP.

chrome/common/page_load_metrics/page_load_timing.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/common/page_load_metrics/page_load_timing.h"
 
 namespace page_load_metrics {
 
 StyleSheetTiming::StyleSheetTiming() {}
 
 StyleSheetTiming::StyleSheetTiming(const StyleSheetTiming& other) = default;
 
 StyleSheetTiming::~StyleSheetTiming() {}
 
 bool StyleSheetTiming::operator==(const StyleSheetTiming& other) const {
   return author_style_sheet_parse_duration_before_fcp ==
-         other.author_style_sheet_parse_duration_before_fcp;
+             other.author_style_sheet_parse_duration_before_fcp &&
+         update_style_duration_before_fcp ==
+             other.update_style_duration_before_fcp;
 }
 
 bool StyleSheetTiming::IsEmpty() const {
-  return !author_style_sheet_parse_duration_before_fcp;
+  return !author_style_sheet_parse_duration_before_fcp &&
+         !update_style_duration_before_fcp;
 }
 
 PageLoadTiming::PageLoadTiming() {}
 
 PageLoadTiming::PageLoadTiming(const PageLoadTiming& other) = default;
 
 PageLoadTiming::~PageLoadTiming() {}
 
 bool PageLoadTiming::operator==(const PageLoadTiming& other) const {
   return navigation_start == other.navigation_start &&
@@ skipping 33 matching lines @@
          style_sheet_timing.IsEmpty();
 }
 
 PageLoadMetadata::PageLoadMetadata() {}
 
 bool PageLoadMetadata::operator==(const PageLoadMetadata& other) const {
   return behavior_flags == other.behavior_flags;
 }
 
 }  // namespace page_load_metrics