Revert "Updated MallocHooks to collect stack traces when memory is allocated."

runtime/vm/source_report.cc

Index: runtime/vm/source_report.cc
diff --git a/runtime/vm/source_report.cc b/runtime/vm/source_report.cc
index 1508ae7347a12cf46019b7fd728ce0519402a524..e156203e50365609070416d5463e0c294dbc5bec 100644
--- a/runtime/vm/source_report.cc
+++ b/runtime/vm/source_report.cc
@@ -56,8 +56,8 @@ void SourceReport::Init(Thread* thread,
   ClearScriptTable();
   if (IsReportRequested(kProfile)) {
     // Build the profile.
-    SampleFilter samplesForIsolate(thread_->isolate()->main_port(),
-                                   Thread::kMutatorTask, -1, -1);
+    SampleFilter samplesForIsolate(thread_->isolate(), Thread::kMutatorTask, -1,
+                                   -1);
     profile_.Build(thread, &samplesForIsolate, Profile::kNoTags);
   }
 }