[tracing] Add native allocation tracing mode.

base/trace_event/heap_profiler_allocation_context.h

Index: base/trace_event/heap_profiler_allocation_context.h
diff --git a/base/trace_event/heap_profiler_allocation_context.h b/base/trace_event/heap_profiler_allocation_context.h
index 70ec7596661c8b2100e6d8083dbaddab36c0a4a7..04ed180cd181cef1a42d44f73408ebe230e1e800 100644
--- a/base/trace_event/heap_profiler_allocation_context.h
+++ b/base/trace_event/heap_profiler_allocation_context.h
@@ -44,6 +44,7 @@ struct BASE_EXPORT StackFrame {
   enum class Type {
     TRACE_EVENT_NAME,   // const char* string
     THREAD_NAME,        // const char* thread name
+    PROGRAM_COUNTER,    // as returned by stack tracing (e.g. by StackTrace)
   };
 
   static StackFrame FromTraceEventName(const char* name) {
@@ -52,6 +53,9 @@ struct BASE_EXPORT StackFrame {
   static StackFrame FromThreadName(const char* name) {
     return {Type::THREAD_NAME, name};
   }
+  static StackFrame FromProgramCounter(const void* pc) {
+    return {Type::PROGRAM_COUNTER, pc};
+  }
 
   Type type;
   const void* value;