memory-infra: Fill the memory dump callback result (1/2)

base/trace_event/memory_allocator_dump.h

 // Copyright 2015 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 BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_
 #define BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 45 matching lines @@
   // - "size" column (all dumps are expected to have at least this one):
   //     AddScalar(kNameSize, kUnitsBytes, 1234);
   // - Some extra-column reporting internal details of the subsystem:
   //    AddScalar("number_of_freelist_entires", kUnitsObjects, 42)
   // - Other informational column (will not be auto-added in the UI)
   //    AddScalarF("kittens_ratio", "ratio", 42.0f)
   void AddScalar(const char* name, const char* units, uint64_t value);
   void AddScalarF(const char* name, const char* units, double value);
   void AddString(const char* name, const char* units, const std::string& value);
 
+  // Get the size for this dump.
+  // The size is the value set with AddScalar(kNameSize, kUnitsBytes, size);
+  uint64_t GetSize();

[Primiano Tucci (use gerrit), 2017/03/22 17:19:52]

can you plz:
- make this private (or protected, if it helps from a documentation viewpoint)
- make MDM a friend of this class
- Add a TODO(hjd) explaining that this is transitional, untile we get to the
state where the full PMD can be sent over IPC/MOJO (better if you file a bug
explaining this and link it to the todo) 

[hjd, 2017/03/22 19:24:20]

Done.

+
   // Absolute name, unique within the scope of an entire ProcessMemoryDump.
   const std::string& absolute_name() const { return absolute_name_; }
 
   // Called at trace generation time to populate the TracedValue.
   void AsValueInto(TracedValue* value) const;
 
   // Use enum Flags to set values.
   void set_flags(int flags) { flags_ |= flags; }
   void clear_flags(int flags) { flags_ &= ~flags; }
   int flags() { return flags_; }
 
   // |guid| is an optional global dump identifier, unique across all processes
   // within the scope of a global dump. It is only required when using the
   // graph APIs (see TODO_method_name) to express retention / suballocation or
   // cross process sharing. See crbug.com/492102 for design docs.
   // Subsequent MemoryAllocatorDump(s) with the same |absolute_name| are
   // expected to have the same guid.
   const MemoryAllocatorDumpGuid& guid() const { return guid_; }
 
   TracedValue* attributes_for_testing() const { return attributes_.get(); }
 
  private:
   const std::string absolute_name_;
   ProcessMemoryDump* const process_memory_dump_;  // Not owned (PMD owns this).
   std::unique_ptr<TracedValue> attributes_;
   MemoryAllocatorDumpGuid guid_;
   int flags_;  // See enum Flags.
+  uint64_t size_;
 
   // A local buffer for Sprintf conversion on fastpath. Avoids allocating
   // temporary strings on each AddScalar() call.
   std::string string_conversion_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryAllocatorDump);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_