Improvements to uses of base::SmallMap

ui/latency/latency_info.h

 // Copyright 2013 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.
 
 #ifndef UI_LATENCY_LATENCY_INFO_H_
 #define UI_LATENCY_LATENCY_INFO_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
-#include "base/containers/small_map.h"
+#include "base/containers/flat_map.h"
 #include "base/time/time.h"
 #include "ui/gfx/geometry/point_f.h"
 
 #if !defined(OS_IOS)
 #include "ipc/ipc_param_traits.h"  // nogncheck
 #include "mojo/public/cpp/bindings/struct_traits.h"  // nogncheck
 #endif
 
 namespace base {
 namespace trace_event {
@@ skipping 97 matching lines @@
     // Average time of events that happened in this component.
     base::TimeTicks event_time;
     // Count of events that happened in this component
     uint32_t event_count;
     // Time of the oldest event that happened in this component.
     base::TimeTicks first_event_time;
     // Time of the most recent event that happened in this component.
     base::TimeTicks last_event_time;
   };
 
-  // Empirically determined constant based on a typical scroll sequence.
-  enum { kTypicalMaxComponentsPerLatencyInfo = 10 };
-
   enum : size_t { kMaxInputCoordinates = 2 };
 
   // Map a Latency Component (with a component-specific int64_t id) to a
   // component info.
-  typedef base::SmallMap<
-      std::map<std::pair<LatencyComponentType, int64_t>, LatencyComponent>,
-      kTypicalMaxComponentsPerLatencyInfo> LatencyMap;
+  using LatencyMap = base::flat_map<std::pair<LatencyComponentType, int64_t>,
+                                    LatencyComponent>;
 
   LatencyInfo();
   LatencyInfo(const LatencyInfo& other);
   LatencyInfo(SourceEventType type);
   ~LatencyInfo();
 
   // For test only.
   LatencyInfo(int64_t trace_id, bool terminated);
 
   // Returns true if the vector |latency_info| is valid. Returns false
@@ skipping 112 matching lines @@
 
 // This is declared here for use in gtest-based unit tests, but is defined in
 // //ui/latency:test_support target.
 // Without this the default PrintTo template in gtest tries to pass LatencyInfo
 // by value, which leads to an alignment compile error on Windows.
 void PrintTo(const LatencyInfo& latency, ::std::ostream* os);
 
 }  // namespace ui
 
 #endif  // UI_LATENCY_LATENCY_INFO_H_