Populate initial base info with unknown state values

Set the current state key to a HashableDimensionKey with -1
(kStateUnknown) for each sliced state atom. Previously, the current
state key was being set to the DEFAULT_DIMENSION_KEY which is an empty
HashableDimensionKey.

Bug: 155487198
Test: make statsd_test && adb sync data && adb shell
data/nativetest/statsd_test/statsd_test

Change-Id: Icaa187ecae599407695d86eec6104d210aa98714
diff --git a/cmds/statsd/src/metrics/MetricProducer.cpp b/cmds/statsd/src/metrics/MetricProducer.cpp
index 2518d85..bb4f03e 100644
--- a/cmds/statsd/src/metrics/MetricProducer.cpp
+++ b/cmds/statsd/src/metrics/MetricProducer.cpp
@@ -293,6 +293,17 @@
     }
 }
 
+HashableDimensionKey MetricProducer::getUnknownStateKey() {
+    HashableDimensionKey stateKey;
+    for (auto atom : mSlicedStateAtoms) {
+        FieldValue fieldValue;
+        fieldValue.mField.setTag(atom);
+        fieldValue.mValue.setInt(StateTracker::kStateUnknown);
+        stateKey.addValue(fieldValue);
+    }
+    return stateKey;
+}
+
 DropEvent MetricProducer::buildDropEvent(const int64_t dropTimeNs, const BucketDropReason reason) {
     DropEvent event;
     event.reason = reason;