SurfaceFlingerPerfTests: Buffer clean up for SurfaceFlingerPerfTests.

Added freeBuffers() function which will be called at the end of tests. It destroys all buffers in queue instead of waiting for GC to clean up.

Test: atest SurfaceFlingerPerfTests
Bug: b/230039226
Change-Id: I28e280b8df2d7140fb51fb05fd4e897e23478143

apct-tests/perftests/surfaceflinger/src/android/surfaceflinger/BufferFlinger.java

@@ -70,4 +70,10 @@ public class BufferFlinger {
         }
         mBufferQ.add(buffer);
     }
+
+    public void freeBuffers() {
+        for (GraphicBuffer buffer : mBufferQ) {
+            buffer.destroy();
+        }
+    }
 }

apct-tests/perftests/surfaceflinger/src/android/surfaceflinger/SurfaceFlingerPerfTest.java

@@ -60,6 +60,7 @@ public class SurfaceFlingerPerfTest {
             bufferflinger.addBuffer(t, sc);
             t.apply();
         }
+        bufferflinger.freeBuffers();
     }
 }