Instrument parser blocking script execution time.

chrome/browser/page_load_metrics/metrics_web_contents_observer.cc

Index: chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
diff --git a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
index dd8e82fe0321540735ca4e02d5b73db77a579c6c..0b7ce65aafc07a6c00a9bc7c8974cac8b67ef5fd 100644
--- a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
+++ b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
@@ -115,6 +115,12 @@ bool IsValidPageLoadTiming(const PageLoadTiming& timing) {
                    << " for parse duration " << parse_duration;
       return false;
     }
+    if (timing.parse_blocked_on_script_execution_duration > parse_duration) {
+      NOTREACHED() << "Invalid parse_blocked_on_script_execution_duration "
+                   << timing.parse_blocked_on_script_execution_duration
+                   << " for parse duration " << parse_duration;
+      return false;
+    }
   }
 
   if (timing.parse_blocked_on_script_load_from_document_write_duration >
@@ -127,6 +133,17 @@ bool IsValidPageLoadTiming(const PageLoadTiming& timing) {
     return false;
   }
 
+  if (timing.parse_blocked_on_script_execution_from_document_write_duration >
+      timing.parse_blocked_on_script_execution_duration) {
+    NOTREACHED()
+        << "Invalid "
+           "parse_blocked_on_script_execution_from_document_write_duration "
+        << timing.parse_blocked_on_script_execution_from_document_write_duration
+        << " for parse_blocked_on_script_execution_duration "
+        << timing.parse_blocked_on_script_execution_duration;
+    return false;
+  }
+
   if (!EventsInOrder(timing.parse_stop,
                      timing.dom_content_loaded_event_start)) {
     NOTREACHED() << "Invalid parse_stop " << timing.parse_stop