Make loader lock new-allocated to avoid shutdown crash.

runtime/bin/loader.cc

Index: runtime/bin/loader.cc
diff --git a/runtime/bin/loader.cc b/runtime/bin/loader.cc
index 8e24f677719e5ab95db8c388dabd1e339b87dd87..b4d50a0b2fd80619f6b624c31c34f21030ef8f2e 100644
--- a/runtime/bin/loader.cc
+++ b/runtime/bin/loader.cc
@@ -608,7 +608,12 @@ Dart_Handle Loader::DartColonLibraryTagHandler(Dart_LibraryTag tag,
 }
 
 
-Mutex Loader::loader_infos_lock_;
+void Loader::InitOnce() {
+  loader_infos_lock_ = new Mutex();

[zra, 2016/07/13 14:51:38]

Can this be deleted in a Loader::Shutdown() call somewhere in Dart::Cleanup()?

[Florian Schneider, 2016/07/13 16:13:58]

It could be. But since it is in the embedder, and only called before they whole
VM exits, there's no leak - and it won't be called from Process::Exit either.

I'd rather don't delete, because then I don't have to worry about potential
use-after-free.

[zra, 2016/07/13 16:16:06]

sgtm. Didn't notice this was in bin/

+}
+
+
+Mutex* Loader::loader_infos_lock_;
 Loader::LoaderInfo* Loader::loader_infos_ = NULL;
 intptr_t Loader::loader_infos_length_ = 0;
 intptr_t Loader::loader_infos_capacity_ = 0;
@@ -619,7 +624,7 @@ intptr_t Loader::loader_infos_capacity_ = 0;
 // correct loader.
 // This happens whenever an isolate begins loading.
 void Loader::AddLoader(Dart_Port port, IsolateData* isolate_data) {
-  MutexLocker ml(&loader_infos_lock_);
+  MutexLocker ml(loader_infos_lock_);
   ASSERT(LoaderForLocked(port) == NULL);
   if (loader_infos_length_ == loader_infos_capacity_) {
     // Grow to an initial capacity or double in size.
@@ -647,7 +652,7 @@ void Loader::AddLoader(Dart_Port port, IsolateData* isolate_data) {
 // Remove |port| from the map.
 // This happens once an isolate has finished loading.
 void Loader::RemoveLoader(Dart_Port port) {
-  MutexLocker ml(&loader_infos_lock_);
+  MutexLocker ml(loader_infos_lock_);
   const intptr_t index = LoaderIndexFor(port);
   ASSERT(index >= 0);
   const intptr_t last = loader_infos_length_ - 1;
@@ -680,14 +685,14 @@ Loader* Loader::LoaderForLocked(Dart_Port port) {
 
 
 Loader* Loader::LoaderFor(Dart_Port port) {
-  MutexLocker ml(&loader_infos_lock_);
+  MutexLocker ml(loader_infos_lock_);
   return LoaderForLocked(port);
 }
 
 
 void Loader::NativeMessageHandler(Dart_Port dest_port_id,
                                   Dart_CObject* message) {
-  MutexLocker ml(&loader_infos_lock_);
+  MutexLocker ml(loader_infos_lock_);
   Loader* loader = LoaderForLocked(dest_port_id);
   if (loader == NULL) {
     return;