[tracing] Introduce support for userland memory allocators dumps.

base/trace_event/process_memory_dump.h

Index: base/trace_event/process_memory_dump.h
diff --git a/base/trace_event/process_memory_dump.h b/base/trace_event/process_memory_dump.h
index 4256c4cadc81340bf05c7d7ea54e25d366f7a93d..81d52f4bf1ff8674a95795b89a283279e8eb7838 100644
--- a/base/trace_event/process_memory_dump.h
+++ b/base/trace_event/process_memory_dump.h
@@ -6,6 +6,10 @@
 #define BASE_TRACE_EVENT_PROCESS_MEMORY_DUMP_H_
 
 #include "base/base_export.h"
+#include "base/containers/hash_tables.h"
+#include "base/containers/small_map.h"
+#include "base/memory/scoped_vector.h"
+#include "base/trace_event/memory_allocator_dump.h"
 #include "base/trace_event/process_memory_maps.h"
 #include "base/trace_event/process_memory_totals.h"
 
@@ -13,6 +17,7 @@ namespace base {
 namespace trace_event {
 
 class ConvertableToTraceFormat;
+class MemoryDumpManager;
 
 // ProcessMemoryDump is as a strongly typed container which enforces the data
 // model for each memory dump point and holds the dumps produced by the
@@ -22,6 +27,9 @@ class ConvertableToTraceFormat;
 // dump point time.
 class BASE_EXPORT ProcessMemoryDump {
  public:
+  using AllocatorDumpsMap =
+      SmallMap<hash_map<std::string, MemoryAllocatorDump*>>;
+
   ProcessMemoryDump();
   ~ProcessMemoryDump();
 
@@ -36,6 +44,30 @@ class BASE_EXPORT ProcessMemoryDump {
   bool has_process_mmaps() const { return has_process_mmaps_; }
   void set_has_process_mmaps() { has_process_mmaps_ = true; }
 
+  // Creates a new MemoryAllocatorDump with the given name and returns the
+  // empty object back to the caller. The |name| must be unique in the dump.
+  // ProcessMemoryDump handles the memory ownership of the created object.
+  // |parent| can be used to specify a hierarchical relationship of the
+  // allocator dumps.
+  MemoryAllocatorDump* AddAllocatorDump(const std::string& name);

[nduca, 2015/03/12 04:04:10]

Add->Create?

[Primiano Tucci (use gerrit), 2015/03/13 19:39:07]

Done.

+  MemoryAllocatorDump* AddAllocatorDump(const std::string& name,
+                                        MemoryAllocatorDump* parent);
+
+  // Returns a MemoryAllocatorDump given its name or nullptr if not found.
+  MemoryAllocatorDump* GetAllocatorDump(const std::string& name) const;
+
+  // Returns the map of the MemoryAllocatorDumps added to this dump.
+  const AllocatorDumpsMap& allocator_dumps() const { return allocator_dumps_; }
+
+ protected:
+  // TODO(primiano): remove this once crbug.com/466121 gets fixed (see similar
+  // comment in memory_dump_manager.cc) for more context.
+  friend class MemoryDumpManager;
+  MemoryAllocatorDump* last_allocator_dump() const {
+    return allocator_dumps_storage_.empty() ? nullptr
+                                            : allocator_dumps_storage_.back();
+  }
+
  private:
   ProcessMemoryTotals process_totals_;
   bool has_process_totals_;
@@ -43,6 +75,13 @@ class BASE_EXPORT ProcessMemoryDump {
   ProcessMemoryMaps process_mmaps_;
   bool has_process_mmaps_;
 
+  // A maps of "allocator_name" -> MemoryAllocatorDump populated by
+  // allocator dump providers.
+  AllocatorDumpsMap allocator_dumps_;
+
+  // ProcessMemoryDump handles the memory ownership of all its belongings.
+  ScopedVector<MemoryAllocatorDump> allocator_dumps_storage_;
+
   DISALLOW_COPY_AND_ASSIGN(ProcessMemoryDump);
 };