Updated MallocHooks to collect stack traces when memory is allocated.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 916e81bb14824779a26edcc42172197091448e00..19c6a32ce33b87cfc19efba40ffa4c2924f4712a 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -152,7 +152,6 @@ char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
   start_time_micros_ = OS::GetCurrentMonotonicMicros();
   VirtualMemory::InitOnce();
   OSThread::InitOnce();
-  MallocHooks::InitOnce();
   if (FLAG_support_timeline) {
     Timeline::InitOnce();
   }
@@ -233,6 +232,7 @@ char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
         return strdup("Precompiled runtime requires a precompiled snapshot");
 #else
         StubCode::InitOnce();
+        MallocHooks::InitOnce();

[zra, 2017/02/08 17:42:55]

What's the reason for moving this around? If it's temporary because of a bug,
you probably want to add a comment with a TODO. If it's permanent, then a
comment explaining why it can't go earlier is probably appropriate.

[bkonyi, 2017/02/09 21:22:46]

The stack trace collection relies on StubCode being initialized, so
MallocHooks::InitOnce() needed to be moved until after that was done.

 #endif
       } else {
         return strdup("Invalid vm isolate snapshot seen");
@@ -271,6 +271,7 @@ char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
 #else
       vm_snapshot_kind_ = Snapshot::kNone;
       StubCode::InitOnce();
+      MallocHooks::InitOnce();
       Symbols::InitOnce(vm_isolate_);
 #endif
     }