NPE recycling null Bitmap

[sjudd]

Internal bug is b/18093433.

Not totally clear how this would happen, I'll start by adding assertions that data is not null when resources are created.

E/AndroidRuntime(  506): FATAL EXCEPTION: main
E/AndroidRuntime(  506): Process: com.android.camera2, PID: 506
E/AndroidRuntime(  506): java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.graphics.Bitmap.isMutable()' on a null object reference
E/AndroidRuntime(  506):        at com.bumptech.glide.load.engine.bitmap_recycle.LruBitmapPool.put(LruBitmapPool.java:65)
E/AndroidRuntime(  506):        at com.bumptech.glide.load.resource.bitmap.BitmapResource.recycle(BitmapResource.java:32)
E/AndroidRuntime(  506):        at com.bumptech.glide.load.engine.EngineResource.recycle(EngineResource.java:57)
E/AndroidRuntime(  506):        at com.bumptech.glide.load.engine.Engine$ResourceRecyclerCallback.handleMessage(Engine.java:273)
E/AndroidRuntime(  506):        at android.os.Handler.dispatchMessage(Handler.java:98)
E/AndroidRuntime(  506):        at android.os.Looper.loop(Looper.java:135)
E/AndroidRuntime(  506):        at android.app.ActivityThread.main(ActivityThread.java:5221)
E/AndroidRuntime(  506):        at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(  506):        at java.lang.reflect.Method.invoke(Method.java:372)
E/AndroidRuntime(  506):        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
E/AndroidRuntime(  506):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
W/ActivityManager(  758):   Force finishing activity com.android.camera2/com.android.camera.CameraLauncher

[sjudd]

I believe the earlier commits fixed the recycling problem and have revealed the underlying cause. When the drawable is stopped and then started again while a frame is being decoded (via start/stop or setVisible), the decoder is advanced and a second frame decode may be started simultaneously using the same GifDecoder, resulting in the error below.

D/GenericRequest( 6031): load failed
D/GenericRequest( 6031): java.lang.ArrayIndexOutOfBoundsException: length=4097; index=4097
D/GenericRequest( 6031):        at com.bumptech.glide.gifdecoder.GifDecoder.decodeBitmapData(GifDecoder.java:616)
D/GenericRequest( 6031):        at com.bumptech.glide.gifdecoder.GifDecoder.setPixels(GifDecoder.java:450)
D/GenericRequest( 6031):        at com.bumptech.glide.gifdecoder.GifDecoder.getNextFrame(GifDecoder.java:294)
D/GenericRequest( 6031):        at com.bumptech.glide.load.resource.gif.GifFrameResourceDecoder.decode(GifFrameResourceDecoder.java:19)
D/GenericRequest( 6031):        at com.bumptech.glide.load.resource.gif.GifFrameResourceDecoder.decode(GifFrameResourceDecoder.java:10)
D/GenericRequest( 6031):        at com.bumptech.glide.load.engine.DecodeJob.decodeFromSourceData(DecodeJob.java:143)
D/GenericRequest( 6031):        at com.bumptech.glide.load.engine.DecodeJob.decodeSource(DecodeJob.java:131)
D/GenericRequest( 6031):        at com.bumptech.glide.load.engine.DecodeJob.decodeFromSource(DecodeJob.java:101)
D/GenericRequest( 6031):        at com.bumptech.glide.load.engine.EngineRunnable.decodeFromSource(EngineRunnable.java:121)
D/GenericRequest( 6031):        at com.bumptech.glide.load.engine.EngineRunnable.decode(EngineRunnable.java:100)
D/GenericRequest( 6031):        at com.bumptech.glide.load.engine.EngineRunnable.run(EngineRunnable.java:57)
D/GenericRequest( 6031):        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
D/GenericRequest( 6031):        at java.util.concurrent.FutureTask.run(FutureTask.java:237)
D/GenericRequest( 6031):        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
D/GenericRequest( 6031):        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
D/GenericRequest( 6031):        at java.lang.Thread.run(Thread.java:841)