Cleanup app snapshots on isolate/vm exit.

runtime/bin/extensions_macos.cc

Index: runtime/bin/extensions_macos.cc
diff --git a/runtime/bin/extensions_macos.cc b/runtime/bin/extensions_macos.cc
index d994c17bd163aae0dbaf704952d8f343ceb83982..f65a04527da6fccf05e2e940c8b3fe1a2f73ae78 100644
--- a/runtime/bin/extensions_macos.cc
+++ b/runtime/bin/extensions_macos.cc
@@ -8,6 +8,8 @@
 #include "bin/extensions.h"
 #include <dlfcn.h>  // NOLINT
 
+#include "platform/assert.h"
+
 namespace dart {
 namespace bin {
 
@@ -17,15 +19,24 @@ const char* kIsolateSnapshotDataSymbolName = "kDartIsolateSnapshotData";
 const char* kIsolateSnapshotInstructionsSymbolName =
     "kDartIsolateSnapshotInstructions";
 
-void* Extensions::LoadExtensionLibrary(const char* library_file) {
+void* Extensions::LoadLibrary(const char* library_file) {
   return dlopen(library_file, RTLD_LAZY);
 }
 
+
 void* Extensions::ResolveSymbol(void* lib_handle, const char* symbol) {
   dlerror();
   return dlsym(lib_handle, symbol);
 }
 
+
+void Extensions::UnloadLibrary(void* lib_handle) {
+  dlerror();
+  int result = dlclose(lib_handle);
+  ASSERT(result == 0);
+}
+
+
 Dart_Handle Extensions::GetError() {
   const char* err_str = dlerror();
   if (err_str != NULL) {