Log histogram of unwind timing.

Test: profile, get go/heapprofd-example-histogram as output.

Bug: 129054982

Change-Id: I46c3646ddd125fb5e8e436fe16070866c916aaff
diff --git a/Android.bp b/Android.bp
index 85af40d..cae2de6 100644
--- a/Android.bp
+++ b/Android.bp
@@ -2897,6 +2897,7 @@
     "src/profiling/memory/client.cc",
     "src/profiling/memory/client_unittest.cc",
     "src/profiling/memory/heapprofd_producer.cc",
+    "src/profiling/memory/heapprofd_producer_unittest.cc",
     "src/profiling/memory/interner_unittest.cc",
     "src/profiling/memory/proc_utils.cc",
     "src/profiling/memory/proc_utils_unittest.cc",