Add CSSTiming to collect aggregate PLT-level stats about CSS.

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 {
 
 PageLoadTiming::PageLoadTiming() {}
 
@@ skipping 15 matching lines @@
          first_meaningful_paint == other.first_meaningful_paint &&
          parse_start == other.parse_start && parse_stop == other.parse_stop &&
          parse_blocked_on_script_load_duration ==
              other.parse_blocked_on_script_load_duration &&
          parse_blocked_on_script_load_from_document_write_duration ==
              other.parse_blocked_on_script_load_from_document_write_duration &&
          parse_blocked_on_script_execution_duration ==
              other.parse_blocked_on_script_execution_duration &&
          parse_blocked_on_script_execution_from_document_write_duration ==
              other
-                 .parse_blocked_on_script_execution_from_document_write_duration;
+                 .parse_blocked_on_script_execution_from_document_write_duration &&
+         author_style_sheet_parse_duration_before_fcp ==
+             other.author_style_sheet_parse_duration_before_fcp;
 }
 
 bool PageLoadTiming::IsEmpty() const {
   return navigation_start.is_null() && !response_start &&
          !dom_content_loaded_event_start && !load_event_start &&
          !first_layout && !first_paint && !first_text_paint &&
          !first_image_paint && !first_contentful_paint &&
          !first_meaningful_paint && !parse_start && !parse_stop &&
          !parse_blocked_on_script_load_duration &&
          !parse_blocked_on_script_load_from_document_write_duration &&
          !parse_blocked_on_script_execution_duration &&
-         !parse_blocked_on_script_execution_from_document_write_duration;
+         !parse_blocked_on_script_execution_from_document_write_duration &&
+         !author_style_sheet_parse_duration_before_fcp;
 }
 
 PageLoadMetadata::PageLoadMetadata() {}
 
 bool PageLoadMetadata::operator==(const PageLoadMetadata& other) const {
   return behavior_flags == other.behavior_flags;
 }
 
 }  // namespace page_load_metrics