trace_processor: implement first android mem metric!

We fill the LMK field for now: more metrics will be filled in following
CLs.

Context: go/perfetto-metrics
Bug: 129747127
Change-Id: If3d7de375e16bbfd15a8b19bda05d3162ae30308
diff --git a/src/trace_processor/trace_processor_shell.cc b/src/trace_processor/trace_processor_shell.cc
index 05215e4..a75d934 100644
--- a/src/trace_processor/trace_processor_shell.cc
+++ b/src/trace_processor/trace_processor_shell.cc
@@ -17,6 +17,7 @@
 #include <aio.h>
 #include <fcntl.h>
 #include <inttypes.h>
+#include <stdio.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
@@ -248,6 +249,7 @@
     PERFETTO_ELOG("Error when computing metrics");
     return 1;
   }
+  fwrite(metric_result.data(), sizeof(uint8_t), metric_result.size(), stdout);
   return 0;
 }