Allow linux trace events to not be time-shifted.

chrome/browser/resources/tracing/linux_perf_importer.js

Index: chrome/browser/resources/tracing/linux_perf_importer.js
diff --git a/chrome/browser/resources/tracing/linux_perf_importer.js b/chrome/browser/resources/tracing/linux_perf_importer.js
index 56c77a2863dbc4fa184a6fef31aa66ddcdb5eaf6..ffeb5a732b3d09eb00bea37f6af60b6badbb8e92 100644
--- a/chrome/browser/resources/tracing/linux_perf_importer.js
+++ b/chrome/browser/resources/tracing/linux_perf_importer.js
@@ -312,6 +312,10 @@ cr.define('tracing', function() {
 
       // Shift all the slice times based on the sync record.
       var sync = this.clockSyncRecords_[0];
+      // NB: parentTS of zero denotes no times-shift; this is
+      // used when user and kernel event clocks are identical.
+      if (sync.parentTS == 0 || sync.parentTS == sync.perfTS)
+        return true;
       var timeShift = sync.parentTS - sync.perfTS;
       for (var cpuNumber in this.cpuStates_) {
         var cpuState = this.cpuStates_[cpuNumber];