Fix a deadlock in EngineResource/Engine.

Engine acquires it's lock, then the EngineResource lock when it loads
resources from cache or active resources. EngineResource acquires its
lock, then the EngineLock, when a resource is cleared. This conflicting
lock order leads to deadlock.

The fix is similar to the fix applied in ActiveResources. We always make
sure that the Engine (listener) lock is acquired before the
EngineResource lock.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=233861929

library/src/main/java/com/bumptech/glide/load/engine/EngineResource.java

@@ -13,11 +13,12 @@
 class EngineResource<Z> implements Resource<Z> {
   private final boolean isCacheable;
   private final boolean isRecyclable;
+  private final Resource<Z> resource;
+
   private ResourceListener listener;
   private Key key;
   private int acquired;
   private boolean isRecycled;
-  private final Resource<Z> resource;
 
   interface ResourceListener {
     void onResourceReleased(Key key, EngineResource<?> resource);
@@ -97,12 +98,21 @@ synchronized void acquire() {
    * done with the resource. Generally external users should never call this method, the framework
    * will take care of this for you.
    */
-  synchronized void release() {
-    if (acquired <= 0) {
-      throw new IllegalStateException("Cannot release a recycled or not yet acquired resource");
-    }
-    if (--acquired == 0) {
-      listener.onResourceReleased(key, this);
+  // listener is effectively final.
+  @SuppressWarnings("SynchronizeOnNonFinalField")
+  void release() {
+    // To avoid deadlock, always acquire the listener lock before our lock so that the locking
+    // scheme is consistent (Engine -> EngineResource). Violating this order leads to deadlock
+    // (b/123646037).
+    synchronized (listener) {
+      synchronized (this) {
+        if (acquired <= 0) {
+          throw new IllegalStateException("Cannot release a recycled or not yet acquired resource");
+        }
+        if (--acquired == 0) {
+          listener.onResourceReleased(key, this);
+        }
+      }
     }
   }