[tracing] Switch to new heap dump format.

base/trace_event/heap_profiler_type_name_deduplicator.cc

Index: base/trace_event/heap_profiler_type_name_deduplicator.cc
diff --git a/base/trace_event/heap_profiler_type_name_deduplicator.cc b/base/trace_event/heap_profiler_type_name_deduplicator.cc
index a6dab51ad2abf24195a76c7f47b4dc0151fc99f7..a804033dc239d613123053aedb562676730b8a77 100644
--- a/base/trace_event/heap_profiler_type_name_deduplicator.cc
+++ b/base/trace_event/heap_profiler_type_name_deduplicator.cc
@@ -9,11 +9,10 @@
 #include <string>
 #include <utility>
 
-#include "base/json/string_escape.h"
 #include "base/strings/string_split.h"
-#include "base/strings/stringprintf.h"
 #include "base/trace_event/memory_usage_estimator.h"
 #include "base/trace_event/trace_event.h"
+#include "base/trace_event/trace_event_argument.h"
 #include "base/trace_event/trace_event_memory_overhead.h"
 
 namespace base {
@@ -56,7 +55,7 @@ StringPiece ExtractCategoryFromTypeName(const char* type_name) {
 
 TypeNameDeduplicator::TypeNameDeduplicator() {
   // A null pointer has type ID 0 ("unknown type");
-  type_ids_.insert(std::make_pair(nullptr, 0));
+  Insert(nullptr);
 }
 
 TypeNameDeduplicator::~TypeNameDeduplicator() {}
@@ -70,38 +69,26 @@ int TypeNameDeduplicator::Insert(const char* type_name) {
     // The type IDs are assigned sequentially and they are zero-based, so
     // |size() - 1| is the ID of the new element.
     elem->second = static_cast<int>(type_ids_.size() - 1);
+    new_type_ids_.push_back(result.first);
   }
 
   return elem->second;
 }
 
-void TypeNameDeduplicator::AppendAsTraceFormat(std::string* out) const {
-  out->append("{");  // Begin the type names dictionary.
+void TypeNameDeduplicator::AppendIncrementally(TracedValue* traced_value) {
+  for (const auto& name_and_id : new_type_ids_) {
+    traced_value->BeginDictionary();
 
-  auto it = type_ids_.begin();
-  std::string buffer;
-
-  // Write the first entry manually; the null pointer must not be dereferenced.
-  // (The first entry is the null pointer because a |std::map| is ordered.)
-  it++;
-  out->append("\"0\":\"[unknown]\"");
-
-  for (; it != type_ids_.end(); it++) {
-    // Type IDs in the trace are strings, write them as stringified keys of
-    // a dictionary.
-    SStringPrintf(&buffer, ",\"%d\":", it->second);
+    traced_value->SetInteger("id", name_and_id->second);
 
     // TODO(ssid): crbug.com/594803 the type name is misused for file name in
     // some cases.
-    StringPiece type_info = ExtractCategoryFromTypeName(it->first);
+    traced_value->SetString("type",
+                            ExtractCategoryFromTypeName(name_and_id->first));
 
-    // |EscapeJSONString| appends, it does not overwrite |buffer|.
-    bool put_in_quotes = true;
-    EscapeJSONString(type_info, put_in_quotes, &buffer);
-    out->append(buffer);
+    traced_value->EndDictionary();
   }
-
-  out->append("}");  // End the type names dictionary.
+  new_type_ids_.clear();
 }
 
 void TypeNameDeduplicator::EstimateTraceMemoryOverhead(