Add option to gen_snapshot for creating a Makefile describing a snapshot's dependencies.

runtime/bin/vmservice/loader.dart

 // Copyright (c) 2015, 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.
 
 part of vmservice_io;
 
 _sanitizeWindowsPath(path) {
   // For Windows we need to massage the paths a bit according to
   // http://blogs.msdn.com/b/ie/archive/2006/12/06/file-uris-in-windows.aspx
   //
@@ skipping 935 matching lines @@
 const _Dart_kScriptTag = 1;            // Load the root script.
 const _Dart_kSourceTag = 2;            // Load a part source.
 const _Dart_kImportTag = 3;            // Import a library.
 
 // Extra requests. Keep these in sync between loader.dart and builtin.dart.
 const _Dart_kInitLoader = 4;           // Initialize the loader.
 const _Dart_kResourceLoad = 5;         // Resource class support.
 const _Dart_kGetPackageRootUri = 6;    // Uri of the packages/ directory.
 const _Dart_kGetPackageConfigUri = 7;  // Uri of the .packages file.
 const _Dart_kResolvePackageUri = 8;    // Resolve a package: uri.
+
+// Extra requests. Keep these in sync between loader.dart and loader.cc.
 const _Dart_kImportExtension = 9;      // Import a dart-ext: file.
+const _Dart_kResolveAsFilePath = 10;   // Resolve uri to file path.
 
 // External entry point for loader requests.
 _processLoadRequest(request) {
   assert(request is List);
   assert(request.length > 4);
 
   // Should we trace loading?
   bool traceLoading = request[0];
 
   // This is the sending isolate's Dart_GetMainPortId().
@@ skipping 141 matching lines @@
           });
         break;
         default:
           if (traceLoading) {
             _log('Unknown scheme (${pathUri.scheme}) in $pathUri.');
           }
           _sendExtensionImportResponse(sp, uri, libraryUri, null);
         break;
       }
     break;
+    case _Dart_kResolveAsFilePath:
+      String uri = request[4];
+      Uri resolvedUri = Uri.parse(uri);
+      try {
+        if (resolvedUri.scheme == 'package') {
+          resolvedUri = loaderState._resolvePackageUri(resolvedUri);
+        }
+        if (resolvedUri.scheme == '' || resolvedUri.scheme == 'file') {
+          resolvedUri = loaderState._workingDirectory.resolveUri(resolvedUri);
+          var msg = new List(5);
+          msg[0] = tag;
+          msg[1] = uri;
+          msg[2] = resolvedUri.toString();
+          msg[3] = null;
+          msg[4] = resolvedUri.toFilePath();
+          sp.send(msg);
+        } else {
+          throw "Cannot resolve scheme (${resolvedUri.scheme}) to file path"
+                " for $resolvedUri";
+        }
+      } catch (e) {
+        var msg = new List(5);
+        msg[0] = -tag;
+        msg[1] = uri;
+        msg[2] = resolvedUri.toString();
+        msg[3] = null;
+        msg[4] = e.toString();
+        sp.send(msg);
+      }
+    break;
     default:
       _log('Unknown loader request tag=$tag from $isolateId');
   }
 }