Remove #pragma once. Just from base/ for now.

base/test/trace_event_analyzer.h

 // Copyright (c) 2012 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.
 
 // Use trace_analyzer::Query and trace_analyzer::TraceAnalyzer to search for
 // specific trace events that were generated by the trace_event.h API.
 //
 // Basic procedure:
 // - Get trace events JSON string from base::debug::TraceLog.
 // - Create TraceAnalyzer with JSON string.
@@ skipping 57 matching lines @@
 // Step 4: analyze events, such as checking durations.
 //   for (size_t i = 0; i < events.size(); ++i) {
 //     double duration;
 //     EXPECT_TRUE(events[i].GetAbsTimeToOtherEvent(&duration));
 //     EXPECT_LT(duration, 1000000.0/60.0); // expect less than 1/60 second.
 //   }
 
 
 #ifndef BASE_TEST_TRACE_EVENT_ANALYZER_H_
 #define BASE_TEST_TRACE_EVENT_ANALYZER_H_
-#pragma once
 
 #include <map>
 
 #include "base/debug/trace_event.h"
 #include "base/memory/ref_counted.h"
 
 namespace base {
 class Value;
 }
 
@@ skipping 512 matching lines @@
 
 // Count all matches.
 static inline size_t CountMatches(const TraceEventVector& events,
                                   const Query& query) {
   return CountMatches(events, query, 0u, events.size());
 }
 
 }  // namespace trace_analyzer
 
 #endif  // BASE_TEST_TRACE_EVENT_ANALYZER_H_