EffectBase: Make callback getter/setter atomic

Plain sp<> not thread-safe for concurrent set and get.

Test: AudioEffectTest
Test: AudioPreProcessingTest
Test: BassBoostTest
Test: EnvReverbTest
Test: EqualizerTest
Test: LoudnessEnhancerTest
Test: PresetReverbTest
Test: VirtualizerTest
Test: VisualizerTest
Bug: 190024493
Change-Id: Ic65f8eabe21453aefefbdd0080e66d9cb7184f43
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 47b4b18..8ab72a9 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -1638,7 +1638,7 @@
         detachAuxEffect_l(effect->id());
     }
 
-    sp<EffectChain> chain = effect->callback()->chain().promote();
+    sp<EffectChain> chain = effect->getCallback()->chain().promote();
     if (chain != 0) {
         // remove effect chain if removing last effect
         if (chain->removeEffect_l(effect, release) == 0) {