Evict buffers from idle bufferpool

Evict cached buffers from idle bufferpool in order to reduce memory
consumption.

Bug: 146679370
Test: atest CtsMediaTestCases -- --module-arg CtsMediaTestCases:size:small
Change-Id: Ic23bd36c88e4bed2a3a8f8aa277ae4c8ca89a41c
diff --git a/media/bufferpool/2.0/Accessor.h b/media/bufferpool/2.0/Accessor.h
index 8d02519..8b43301 100644
--- a/media/bufferpool/2.0/Accessor.h
+++ b/media/bufferpool/2.0/Accessor.h
@@ -187,6 +187,8 @@
 
     static void createInvalidator();
 
+    static void createEvictor();
+
 private:
     class Impl;
     std::shared_ptr<Impl> mImpl;