Provide a mechanism for dumping of heap profiles on predefined events.

runtime/vm/heap.cc

Index: runtime/vm/heap.cc
diff --git a/runtime/vm/heap.cc b/runtime/vm/heap.cc
index d2f16159afb2e63da022d3d5fafdd49fb40ba368..9db0ad964a3b835ad6e1cadf47bdbbde80957455 100644
--- a/runtime/vm/heap.cc
+++ b/runtime/vm/heap.cc
@@ -286,6 +286,21 @@ void Heap::Profile(Dart_FileWriteCallback callback, void* stream) const {
 }
 
 
+void Heap::ProfileToFile(const char* filename) const {
+  Dart_FileOpenCallback file_open = Isolate::file_open_callback();
+  ASSERT(file_open != NULL);
+  Dart_FileWriteCallback file_write = Isolate::file_write_callback();
+  ASSERT(file_write != NULL);
+  Dart_FileCloseCallback file_close = Isolate::file_close_callback();
+  ASSERT(file_close != NULL);
+  void* file = (*file_open)(filename);
+  if (file != NULL) {
+    Profile(file_write, file);
+    (*file_close)(file);
+  }
+}
+
+
 const char* Heap::GCReasonToString(GCReason gc_reason) {
   switch (gc_reason) {
     case kNewSpace: