mojo::ArrayTraits: Add Support for Iterators

ui/events/mojo/latency_info_struct_traits.h

 // Copyright 2016 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_EVENTS_MOJO_LATENCY_INFO_STRUCT_TRAITS_H_
 #define UI_EVENTS_MOJO_LATENCY_INFO_STRUCT_TRAITS_H_
 
 #include "ui/events/latency_info.h"
 #include "ui/events/mojo/latency_info.mojom.h"
 #include "ui/gfx/geometry/mojo/geometry_struct_traits.h"
 
 namespace mojo {
 
 using InputCoordinateArray = CArray<gfx::PointF>;
 
 template <>
+struct ArrayTraits<ui::LatencyInfo::LatencyMap> {
+  using Element = ui::LatencyInfo::LatencyMap::value_type;
+  using Iterator = ui::LatencyInfo::LatencyMap::iterator;
+  using ConstIterator = ui::LatencyInfo::LatencyMap::const_iterator;
+
+  static ConstIterator GetBegin(const ui::LatencyInfo::LatencyMap& input) {
+    return input.begin();
+  }
+  static Iterator GetBegin(ui::LatencyInfo::LatencyMap& input) {
+    return input.begin();
+  }
+
+  static void AdvanceIterator(ConstIterator& iterator) { iterator++; }
+  static void AdvanceIterator(Iterator& iterator) { iterator++; }
+
+  static const Element& GetValue(ConstIterator& iterator) { return *iterator; }
+  static Element& GetValue(Iterator& iterator) { return *iterator; }
+
+  static size_t GetSize(const ui::LatencyInfo::LatencyMap& input) {
+    return input.size();
+  }
+  static bool Resize(ui::LatencyInfo::LatencyMap& input, size_t size) {

[yzshen1, 2016/06/11 00:40:27]

It seems this ArrayTraits is not used for deserialization, maybe you can omit
Resize()?
That way if we do need to use it for deserialization, we will know by
compilation errors.

[Fady Samuel, 2016/06/11 16:16:37]

Done.

+    return true;
+  }
+};
+
+template <>
 struct StructTraits<ui::mojom::LatencyComponent,
                     ui::LatencyInfo::LatencyComponent> {
   static int64_t sequence_number(
       const ui::LatencyInfo::LatencyComponent& component);
   static base::TimeTicks event_time(
       const ui::LatencyInfo::LatencyComponent& component);
   static uint32_t event_count(
       const ui::LatencyInfo::LatencyComponent& component);
   static bool Read(ui::mojom::LatencyComponentDataView data,
                    ui::LatencyInfo::LatencyComponent* out);
 };
 
 template <>
+struct StructTraits<ui::mojom::LatencyComponentPair,
+                    ui::LatencyInfo::LatencyMap::value_type> {
+  static const std::pair<ui::LatencyComponentType, int64_t>& key(
+      const ui::LatencyInfo::LatencyMap::value_type& input) {
+    return input.first;
+  }
+
+  static const ui::LatencyInfo::LatencyComponent& value(
+      const ui::LatencyInfo::LatencyMap::value_type& input) {
+    return input.second;
+  }
+
+  // TODO(fsamuel): Figure out how to optimize deserialization.
+};
+
+template <>
 struct StructTraits<ui::mojom::LatencyComponentId,
                     std::pair<ui::LatencyComponentType, int64_t>> {
   static ui::mojom::LatencyComponentType type(
       const std::pair<ui::LatencyComponentType, int64_t>& id);
   static int64_t id(const std::pair<ui::LatencyComponentType, int64_t>& id);
   static bool Read(ui::mojom::LatencyComponentIdDataView data,
                    std::pair<ui::LatencyComponentType, int64_t>* out);
 };
 
 template <>
 struct StructTraits<ui::mojom::LatencyInfo, ui::LatencyInfo> {
-  static void* SetUpContext(const ui::LatencyInfo& info);
-  static void TearDownContext(const ui::LatencyInfo& info, void* context);
   static const std::string& trace_name(const ui::LatencyInfo& info);
-  static mojo::Array<ui::mojom::LatencyComponentPairPtr>& latency_components(
-      const ui::LatencyInfo& info,
-      void* context);
+  static const ui::LatencyInfo::LatencyMap& latency_components(
+      const ui::LatencyInfo& info);
   static uint32_t input_coordinates_size(const ui::LatencyInfo& info);
   static InputCoordinateArray input_coordinates(const ui::LatencyInfo& info);
   static int64_t trace_id(const ui::LatencyInfo& info);
   static bool coalesced(const ui::LatencyInfo& info);
   static bool terminated(const ui::LatencyInfo& info);
   static bool Read(ui::mojom::LatencyInfoDataView data, ui::LatencyInfo* out);
 };
 
 }  // namespace mojo
 
 #endif  // UI_EVENTS_MOJO_LATENCY_INFO_STRUCT_TRAITS_H_