Cleanup app snapshots on isolate/vm exit.

runtime/bin/extensions_win.cc

Index: runtime/bin/extensions_win.cc
diff --git a/runtime/bin/extensions_win.cc b/runtime/bin/extensions_win.cc
index b07bf590130301506211d8c8264b7b9fe1696019..be49910314bcdc84925a3149edf974db391e586c 100644
--- a/runtime/bin/extensions_win.cc
+++ b/runtime/bin/extensions_win.cc
@@ -8,6 +8,7 @@
 #include "bin/extensions.h"
 #include "bin/utils.h"
 #include "bin/utils_win.h"
+#include "platform/assert.h"
 
 namespace dart {
 namespace bin {
@@ -18,7 +19,7 @@ const char* kIsolateSnapshotDataSymbolName = "_kDartIsolateSnapshotData";
 const char* kIsolateSnapshotInstructionsSymbolName =
     "_kDartIsolateSnapshotInstructions";
 
-void* Extensions::LoadExtensionLibrary(const char* library_file) {
+void* Extensions::LoadLibrary(const char* library_file) {
   SetLastError(0);
 
   // Convert to wchar_t string.
@@ -37,6 +38,11 @@ void* Extensions::ResolveSymbol(void* lib_handle, const char* symbol) {
   return GetProcAddress(reinterpret_cast<HMODULE>(lib_handle), symbol);
 }
 
+void Extensions::UnloadLibrary(void* lib_handle) {
+  BOOL result = FreeLibrary(reinterpret_cast<HMODULE>(lib_handle));
+  ASSERT(result);
+}
+
 Dart_Handle Extensions::GetError() {
   int last_error = GetLastError();
   if (last_error != 0) {