reretry ValueMetric implementation and pulling mechanism

Note:
This is for value metric. The default operations is sum the diffs.
The test uses kernel wake lock, which also needs dimension by kernel
wake lock name.

The test is a bit cumbersome as it needs StatsCompanionService to do
the alarm, which is not exact alarm.

The internal state of a slice of bucket would look something like this:

4:ipc0000005e_727_android.hardwar
0      0
4:SensorService_wakelock
40      64
4:ipc0000005c_727_android.hardwar
...

Test: manual test on device.
Change-Id: I2ed0ac7d3c5fcba8b7611d46f38a38ffd8bdc92a
diff --git a/cmds/statsd/src/external/PullDataReceiver.h b/cmds/statsd/src/external/PullDataReceiver.h
new file mode 100644
index 0000000..0d505cb
--- /dev/null
+++ b/cmds/statsd/src/external/PullDataReceiver.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <utils/String16.h>
+#include <unordered_map>
+#include <utils/RefBase.h>
+#include "StatsPuller.h"
+#include "logd/LogEvent.h"
+
+namespace android {
+namespace os {
+namespace statsd {
+
+class PullDataReceiver : virtual public RefBase{
+ public:
+  virtual ~PullDataReceiver() {}
+  virtual void onDataPulled(const std::vector<std::shared_ptr<LogEvent>>& data) = 0;
+};
+
+}  // namespace statsd
+}  // namespace os
+}  // namespace android
\ No newline at end of file