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

tools/testing/dart/android.dart

Index: tools/testing/dart/android.dart
diff --git a/tools/testing/dart/android.dart b/tools/testing/dart/android.dart
index 985f6bc99a7ba67b6313d82698b5f6a753ed5474..96ac6030ab16f79c05dee5588312028992d90ab3 100644
--- a/tools/testing/dart/android.dart
+++ b/tools/testing/dart/android.dart
@@ -193,6 +193,7 @@ class AndroidHelper {
 class AdbDevice {
   static const _adbServerStartupTime = const Duration(seconds: 3);
   String _deviceId;
+  List<String> _cachedData = new List<String>();
 
   String get deviceId => _deviceId;
 
@@ -248,6 +249,18 @@ class AdbDevice {
   }
 
   /**
+   * Upload data to the device only on first use of [remote].
+   */
+  Future pushCachedData(String local, String remote) {
+    if (_cachedData.contains(remote)) {
+      return new Future.value(new AdbCommandResult(
+          "Skipped cached push", "", "", 0, false));
+    }
+    _cachedData.add(remote);
+    return _adbCommand(['push', local, remote]);

[kustermann, 2017/03/19 17:11:05]

This is not quite safe I think: It's possible to run test.py in a way which runs
multiple configurations at the same time, for example:

./tools/test.py -mdebug,release -cprecompiler -rdart_precompiled 

This will run release and debug in one go. It will queue up the commands
randomly, so we can end up in a situation where we run these two commands

pushCachedData('out/ReleaseXARM/file', '/data/local/temp/file')
pushCachedData('out/DebugXARM/file', '/data/local/temp/file')

The first will push the binary, the second would reuse the binary (which is not
safe).

If you just use a Map<Remote, Local> then you can check if the Remote is
up-to-date and do nothing and otherwise push a new local.

+  }
+
+  /**
    * Change permission of directory recursively.
    */
   Future chmod(String mode, Path directory) {
@@ -416,6 +429,7 @@ class AdbDevicePool {
           'No android devices found. '
           'Please make sure "adb devices" shows your device!');
     }
+    print("Found ${devices.length} Android devices.");
     return new AdbDevicePool(devices);
   }