[tracing] Add trace events to key heap profiler functions.

base/trace_event/heap_profiler_event_writer.cc

Index: base/trace_event/heap_profiler_event_writer.cc
diff --git a/base/trace_event/heap_profiler_event_writer.cc b/base/trace_event/heap_profiler_event_writer.cc
index 23fe761f58ac32a32e3c68dceabdc713ae5fa617..c09a1e2a4bd516022f9cb10f4a07e630993bb893 100644
--- a/base/trace_event/heap_profiler_event_writer.cc
+++ b/base/trace_event/heap_profiler_event_writer.cc
@@ -17,6 +17,7 @@
 #include "base/trace_event/heap_profiler_string_deduplicator.h"
 #include "base/trace_event/heap_profiler_type_name_deduplicator.h"
 #include "base/trace_event/sharded_allocation_register.h"
+#include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
 
 namespace base {
@@ -44,6 +45,7 @@ struct AggregationKey {
 std::unique_ptr<TracedValue> SerializeHeapDump(
     const ShardedAllocationRegister& allocation_register,
     HeapProfilerSerializationState* serialization_state) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("memory-infra"), "SerializeHeapDump");
   // Aggregate allocations by {backtrace_id, type_id} key.
   using MetricsMap = std::unordered_map<AggregationKey, AllocationMetrics,
                                         AggregationKey::Hasher>;
@@ -67,9 +69,13 @@ std::unique_ptr<TracedValue> SerializeHeapDump(
         metrics.size += allocation.size;
         metrics.count += 1;
       };
-  allocation_register.VisitAllocations(base::BindRepeating(
-      visit_allocation, base::Unretained(serialization_state),
-      base::Unretained(&metrics_by_key)));
+  {
+    TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("memory-infra"),
+                 "SerializeHeapDump.VisitAllocations");
+    allocation_register.VisitAllocations(base::BindRepeating(
+        visit_allocation, base::Unretained(serialization_state),
+        base::Unretained(&metrics_by_key)));
+  }
 
   auto traced_value = MakeUnique<TracedValue>();
 
@@ -101,6 +107,8 @@ std::unique_ptr<TracedValue> SerializeHeapDump(
 std::unique_ptr<TracedValue> SerializeHeapProfileEventData(
     const SerializedHeapDumpsMap& heap_dumps,
     HeapProfilerSerializationState* serialization_state) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("memory-infra"),
+               "SerializeHeapProfileEventData");
   auto traced_value = MakeUnique<TracedValue>();
 
   // See brief description of the format in the header file.