Avoid heap trims in foreground and audio apps.

Heap trimming the dlmalloc spaces holds their locks causing jank.
Improve diagnostic message to break apart managed and native heap trims and
detail amount of heap advised back to the kernel.

Change-Id: Ic08cf4749342cbd057b162b901d1676bb7e6418b
diff --git a/src/heap.h b/src/heap.h
index 78cbe99..b7fc34d 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -297,7 +297,7 @@
 
   void DumpForSigQuit(std::ostream& os);
 
-  void Trim();
+  size_t Trim();
 
   HeapBitmap* GetLiveBitmap() SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
     return live_bitmap_.get();