[Tracing] Introduce HeapDumpWriter helper class

base/trace_event/process_memory_dump.cc

Index: base/trace_event/process_memory_dump.cc
diff --git a/base/trace_event/process_memory_dump.cc b/base/trace_event/process_memory_dump.cc
index fab111f6da03858c353c98d66c5d348339cb09f1..289baacc6ebd175869048b918f6e1da0277f26eb 100644
--- a/base/trace_event/process_memory_dump.cc
+++ b/base/trace_event/process_memory_dump.cc
@@ -144,6 +144,11 @@ MemoryAllocatorDump* ProcessMemoryDump::GetSharedGlobalAllocatorDump(
   return GetAllocatorDump(GetSharedGlobalAllocatorDumpName(guid));
 }
 
+void ProcessMemoryDump::AddHeapDump(const std::string& absolute_name,
+                                    scoped_refptr<TracedValue> heap_dump) {
+  heap_dumps_[absolute_name] = heap_dump;

[Primiano Tucci (use gerrit), 2015/10/26 11:52:07]

add a DCHECK_EQ(0u, heap_dumps_.count(absolute_name)) ?

[Ruud van Asseldonk, 2015/10/26 14:51:27]

Done.

+}
+
 void ProcessMemoryDump::Clear() {
   if (has_process_totals_) {
     process_totals_.Clear();
@@ -158,6 +163,7 @@ void ProcessMemoryDump::Clear() {
   allocator_dumps_storage_.clear();
   allocator_dumps_.clear();
   allocator_dumps_edges_.clear();
+  heap_dumps_.clear();
 }
 
 void ProcessMemoryDump::TakeAllDumpsFrom(ProcessMemoryDump* other) {
@@ -179,6 +185,9 @@ void ProcessMemoryDump::TakeAllDumpsFrom(ProcessMemoryDump* other) {
                                 other->allocator_dumps_edges_.begin(),
                                 other->allocator_dumps_edges_.end());
   other->allocator_dumps_edges_.clear();
+
+  heap_dumps_.insert(other->heap_dumps_.begin(), other->heap_dumps_.end());
+  other->heap_dumps_.clear();
 }
 
 void ProcessMemoryDump::AsValueInto(TracedValue* value) const {
@@ -201,6 +210,13 @@ void ProcessMemoryDump::AsValueInto(TracedValue* value) const {
     value->EndDictionary();
   }
 
+  if (heap_dumps_.size() > 0) {
+    value->BeginDictionary("heap_dumps");
+    for (auto name_and_dump : heap_dumps_)

[Primiano Tucci (use gerrit), 2015/10/26 11:52:07]

const auto& ?

[Ruud van Asseldonk, 2015/10/26 14:51:27]

Done.

+      value->SetValueWithCopiedName(name_and_dump.first, *name_and_dump.second);
+    value->EndDictionary();  // heap_dumps
+  }
+
   value->BeginArray("allocators_graph");
   for (const MemoryAllocatorDumpEdge& edge : allocator_dumps_edges_) {
     value->BeginDictionary();