test.py: Push dart_precompiled_runtime and process_test once per device instead of once per test.

tools/testing/dart/android.dart

 // Copyright (c) 2013, 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.
 
 library android;
 
 import "dart:async";
 import "dart:convert" show LineSplitter, UTF8;
 import "dart:core";
 import "dart:collection";
@@ skipping 175 matching lines @@
     result.throwIfFailed();
   }
 }
 
 /**
  * Used for communicating with an emulator or with a real device.
  */
 class AdbDevice {
   static const _adbServerStartupTime = const Duration(seconds: 3);
   String _deviceId;
+  Map<String, String> _cachedData = new Map<String, String>();
 
   String get deviceId => _deviceId;
 
   AdbDevice(this._deviceId);
 
   /**
    * Blocks execution until the device is online
    */
   Future waitForDevice() {
     return _adbCommand(['wait-for-device']);
@@ skipping 35 matching lines @@
   }
 
   /**
    * Upload data to the device.
    */
   Future pushData(Path local, Path remote) {
     return _adbCommand(['push', '$local', '$remote']);
   }
 
   /**
+   * Upload data to the device, unless [local] is the same as the most recently
+   * used source for [remote].
+   */
+  Future pushCachedData(String local, String remote) {
+    if (_cachedData[remote] == local) {
+      return new Future.value(new AdbCommandResult(
+          "Skipped cached push", "", "", 0, false));
+    }
+    _cachedData[remote] = local;
+    return _adbCommand(['push', local, remote]);
+  }
+
+  /**
    * Change permission of directory recursively.
    */
   Future chmod(String mode, Path directory) {
     var arguments = ['shell', 'chmod', '-R', mode, '$directory'];
     return _adbCommand(arguments);
   }
 
   /**
    * Install an application on the device.
    */
@@ skipping 148 matching lines @@
   }
 
   static Future<AdbDevicePool> create() async {
     var names = await AdbHelper.listDevices();
     var devices = names.map((id) => new AdbDevice(id)).toList();
     if (devices.length == 0) {
       throw new Exception(
           'No android devices found. '
           'Please make sure "adb devices" shows your device!');
     }
+    print("Found ${devices.length} Android devices.");
     return new AdbDevicePool(devices);
   }
 
   Future<AdbDevice> acquireDevice() async {
     if (_idleDevices.length > 0) {
       return _idleDevices.removeFirst();
     } else {
       var completer = new Completer();
       _waiter.add(completer);
       return completer.future;
     }
   }
 
   void releaseDevice(AdbDevice device) {
     if (_waiter.length > 0) {
       Completer completer = _waiter.removeFirst();
       completer.complete(device);
     } else {
       _idleDevices.add(device);
     }
   }
 }