Revert "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 7a6e869769a840de36295ffe9cdae684639b4f9e..1415cb1750f5946497735fe851ed9c5dbd294969 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -192,6 +192,17 @@ 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);