[Android] Close FlutterRenderer texture image SyncFence objects immediately after waiting on them (flutter#188313)

Each SyncFence may use a file descriptor. But the SyncFences were not
being closed promptly and their file descriptors were not being deleted
until the SyncFences were garbage collected.

If the process is rendering video and creating a SyncFence for each
frame, then it may run out of file descriptor capacity before Java GC
happens.

Fixes flutter#188161

Author: jason-simmons

engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/renderer/FlutterRenderer.java

@@ -785,9 +785,9 @@ private void cleanup() {
     }
 
     @RequiresApi(API_LEVELS.API_33)
-    private void waitOnFence(Image image) {
-      try {
-        SyncFence fence = image.getFence();
+    @VisibleForTesting
+    void waitOnFence(Image image) {
+      try (SyncFence fence = image.getFence()) {
         fence.awaitForever();
       } catch (IOException e) {
         // Drop.
@@ -1066,8 +1066,7 @@ public void pushImage(Image image) {
 
     @RequiresApi(API_LEVELS.API_33)
     private void waitOnFence(Image image) {
-      try {
-        SyncFence fence = image.getFence();
+      try (SyncFence fence = image.getFence()) {
         fence.awaitForever();
       } catch (IOException e) {
         // Drop.

engine/src/flutter/shell/platform/android/test/io/flutter/embedding/engine/renderer/FlutterRendererTest.java

@@ -28,6 +28,7 @@
 import android.graphics.Canvas;
 import android.graphics.Rect;
 import android.graphics.SurfaceTexture;
+import android.hardware.SyncFence;
 import android.media.Image;
 import android.media.ImageReader;
 import android.os.Looper;
@@ -1074,4 +1075,16 @@ public void restoreSurfaceProducers_restoresImageReaderSurfaceProducersAsIfAppli
     assertFalse(imageReaderProducer1.notifiedDestroy);
     assertFalse(imageReaderProducer2.notifiedDestroy);
   }
+
+  @Test
+  public void waitOnFence_closesFence() throws Exception {
+    FlutterRenderer.ImageReaderSurfaceProducer producer =
+        (FlutterRenderer.ImageReaderSurfaceProducer)
+            engineRule.getFlutterEngine().getRenderer().createSurfaceProducer();
+    Image image = mock(Image.class);
+    SyncFence fence = mock(SyncFence.class);
+    when(image.getFence()).thenReturn(fence);
+    producer.waitOnFence(image);
+    verify(fence, times(1)).close();
+  }
 }