Have separate sampler per heap.

This will allow us to have separate sampling rates per heap (e.g. ART
Allocation Tracking could be higher volume, so we want a higher
interval).  This also is necessary if we want to allow clients to report
samples rather than allocations for their heap, because that will cause
that heap to have a separate (implicit) sampler, while all the others
share one.

Bug: 141241849
Bug: 160214819
Test: Profile system_server
Test: atest perfetto_integrationtests
Change-Id: Id949d668df561e7fa23efc6bd1fd92a92cc6c08e
diff --git a/Android.bp b/Android.bp
index 995769c..944f699 100644
--- a/Android.bp
+++ b/Android.bp
@@ -6311,6 +6311,7 @@
   name: "perfetto_src_profiling_memory_client",
   srcs: [
     "src/profiling/memory/client.cc",
+    "src/profiling/memory/sampler.cc",
   ],
 }