Use a single file for app snapshots.

runtime/bin/extensions_win.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/extensions.h"
 #include "bin/utils.h"
 #include "bin/utils_win.h"
 
 namespace dart {
 namespace bin {
 
-const char* kPrecompiledLibraryName = "precompiled.dll";
+const char* kPrecompiledVMIsolateSymbolName = "_kVmIsolateSnapshot";
+const char* kPrecompiledIsolateSymbolName = "_kIsolateSnapshot";
 const char* kPrecompiledInstructionsSymbolName = "_kInstructionsSnapshot";
 const char* kPrecompiledDataSymbolName = "_kDataSnapshot";
 
 void* Extensions::LoadExtensionLibrary(const char* library_file) {
   SetLastError(0);
   return LoadLibraryW(StringUtilsWin::Utf8ToWide(library_file));
 }
 
 void* Extensions::ResolveSymbol(void* lib_handle, const char* symbol) {
   SetLastError(0);
   return GetProcAddress(reinterpret_cast<HMODULE>(lib_handle), symbol);
 }
 
 Dart_Handle Extensions::GetError() {
   int last_error = GetLastError();
   if (last_error != 0) {
     OSError err;
     return Dart_NewApiError(err.message());
   }
   return Dart_Null();
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)