Use a single file for app snapshots.

runtime/bin/dartutils.cc

Index: runtime/bin/dartutils.cc
diff --git a/runtime/bin/dartutils.cc b/runtime/bin/dartutils.cc
index 1415cb1750f5946497735fe851ed9c5dbd294969..7a6e869769a840de36295ffe9cdae684639b4f9e 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -192,17 +192,6 @@ const char* DartUtils::RemoveScheme(const char* url) {
 }
 
 
-void* DartUtils::MapExecutable(const char* name, intptr_t* len) {
-  File* file = File::Open(name, File::kRead);
-  if (file == NULL) {
-    return NULL;
-  }
-  void* addr = file->MapExecutable(len);
-  file->Release();
-  return addr;
-}
-
-
 void* DartUtils::OpenFile(const char* name, bool write) {
   File* file = File::Open(name, write ? File::kWriteTruncate : File::kRead);
   return reinterpret_cast<void*>(file);