Don't rely on external shasum program to calculate sum of the APK.

packages/flutter_tools/lib/src/device.dart

@@ -10,6 +10,7 @@ import 'dart:math';
 
 import 'package:logging/logging.dart';
 import 'package:path/path.dart' as path;
+import 'package:crypto/crypto.dart';
 
 import 'application_package.dart';
 import 'build_configuration.dart';
@@ -695,9 +696,10 @@ class AndroidDevice extends Device {
   }
 
   String _getSourceSha1(ApplicationPackage app) {
-    String sha1 =
-        runCheckedSync(['shasum', '-a', '1', '-p', app.localPath]).split(' ')[0];
-    return sha1;
+    var sha1 = new SHA1();
+    var file = new File(app.localPath);
+    sha1.add(file.readAsBytesSync());
+    return CryptoUtils.bytesToHex(sha1.close());
   }
 
   @override

packages/flutter_tools/pubspec.yaml

@@ -19,6 +19,7 @@ dependencies:
   shelf: ^0.6.2
   test: ">=0.12.4+5 <0.12.5"
   yaml: ^2.1.3
+  crypto: ^0.9.1
 
 dev_dependencies:
   mockito: "^0.10.1"