Add support for dimension, and link with condition and added DurationMetric

Now we support following metrics:
  <Duration> of [app holding a wake lock], while [*this app*] is [in background] [AND] [screen is off]
  [Slice] the output by [app name, wake lock name], with bucket size [30sec]

+ Also added onDumpReport() api in MetricsManager, it can be called from client to fetch the data from
  statsd

+ Also added command line tool to dump the StatsLogReport from all metrics for debugging.

+ Synced proto from google3. with a pending cl (cr/172359050)

TODO: We need to add tons of tests to test the Metrics. I will work on it after this CL so people
can be unblocked.

I locally test the duration metric with wake lock with an app that generates StatsLog events.

Test: statsd_test

      and manual test, and run:

      adb shell cmd stats dump-report
      We have a default config, which contains a metrics to count PROCESS_START event sliced by
      package name.

Change-Id: I4838cc6cf025c143b7e84f43040703a78121fd25
diff --git a/cmds/statsd/src/logd/LogEvent.cpp b/cmds/statsd/src/logd/LogEvent.cpp
index 9fa2baf..032b4b8 100644
--- a/cmds/statsd/src/logd/LogEvent.cpp
+++ b/cmds/statsd/src/logd/LogEvent.cpp
@@ -150,6 +150,29 @@
     }
 }
 
+KeyValuePair LogEvent::GetKeyValueProto(size_t key) const {
+    KeyValuePair pair;
+    pair.set_key(key);
+    // If the value is not valid, return the KeyValuePair without assigning the value.
+    // Caller can detect the error by checking the enum for "one of" proto type.
+    if (key < 1 || (key - 1) >= mElements.size()) {
+        return pair;
+    }
+    key--;
+
+    const android_log_list_element& elem = mElements[key];
+    if (elem.type == EVENT_TYPE_INT) {
+        pair.set_value_int(elem.data.int32);
+    } else if (elem.type == EVENT_TYPE_LONG) {
+        pair.set_value_int(elem.data.int64);
+    } else if (elem.type == EVENT_TYPE_STRING) {
+        pair.set_value_str(elem.data.string);
+    } else if (elem.type == EVENT_TYPE_FLOAT) {
+        pair.set_value_float(elem.data.float32);
+    }
+    return pair;
+}
+
 string LogEvent::ToString() const {
     ostringstream result;
     result << "{ " << mTimestampNs << " (" << mTagId << ")";