[Tracing] Introduce HeapDumpWriter helper class

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 4f7d141104dd3342a26c3263aa2686bf1f20eb5f..3ce9c43118056f12924e558aef27b582d21e6ebf 100644
--- a/base/trace_event/process_memory_dump.h
+++ b/base/trace_event/process_memory_dump.h
@@ -30,6 +30,7 @@ namespace trace_event {
 class ConvertableToTraceFormat;
 class MemoryDumpManager;
 class MemoryDumpSessionState;
+class TracedValue;
 
 // ProcessMemoryDump is as a strongly typed container which holds the dumps
 // produced by the MemoryDumpProvider(s) for a specific process.
@@ -47,6 +48,9 @@ class BASE_EXPORT ProcessMemoryDump {
   using AllocatorDumpsMap =
       SmallMap<hash_map<std::string, MemoryAllocatorDump*>>;
 
+  using HeapDumpsMap =
+      SmallMap<hash_map<std::string, scoped_refptr<TracedValue>>>;
+
 #if defined(COUNT_RESIDENT_BYTES_SUPPORTED)
   // Returns the total bytes resident for a virtual address range, with given
   // |start_address| and |mapped_size|. |mapped_size| is specified in bytes. The
@@ -95,6 +99,12 @@ class BASE_EXPORT ProcessMemoryDump {
   // Returns the map of the MemoryAllocatorDumps added to this dump.
   const AllocatorDumpsMap& allocator_dumps() const { return allocator_dumps_; }
 
+  // Adds a heap dump for the allocator with |absolute_name|. The |TracedValue|
+  // must have the correct format. |trace_event::HeapDumper| will generate such
+  // a value from a |trace_event::AllocationRegister|.
+  void AddHeapDump(const std::string& absolute_name,
+                   scoped_refptr<TracedValue> heap_dump);
+
   // Adds an ownership relationship between two MemoryAllocatorDump(s) with the
   // semantics: |source| owns |target|, and has the effect of attributing
   // the memory usage of |target| to |source|. |importance| is optional and
@@ -155,6 +165,7 @@ class BASE_EXPORT ProcessMemoryDump {
   bool has_process_mmaps_;
 
   AllocatorDumpsMap allocator_dumps_;
+  HeapDumpsMap heap_dumps_;
 
   // ProcessMemoryDump handles the memory ownership of all its belongings.
   ScopedVector<MemoryAllocatorDump> allocator_dumps_storage_;