Enable passthrough mode by default for audio, soundtrigger, and radio

Remove ENABLE_TREBLE flag usage for legacy hal fallback.
Introduce new build flag USE_LEGACY_LOCAL_AUDIO_HAL for fallback.

Bug: 32978887
Test: checked "OK Google" (from standby), Hangouts, YouTube,
      Play Music, fake radio hal + test app
KI: issues when using equializer and virtualuzer in Play Music

Change-Id: I1c279e622c885f799481f1287e0660ca576fcea0
diff --git a/media/libaudiohal/Android.mk b/media/libaudiohal/Android.mk
index deb26b5..58b38a6 100644
--- a/media/libaudiohal/Android.mk
+++ b/media/libaudiohal/Android.mk
@@ -9,9 +9,20 @@
     liblog      \
     libutils
 
-ifeq ($(ENABLE_TREBLE), true)
+ifeq ($(USE_LEGACY_LOCAL_AUDIO_HAL), true)
 
-LOCAL_CFLAGS += -DENABLE_TREBLE
+# Use audiohal directly w/o hwbinder middleware.
+# This is for performance comparison and debugging only.
+
+LOCAL_SRC_FILES := \
+    DeviceHalLocal.cpp          \
+    DevicesFactoryHalLocal.cpp  \
+    EffectBufferHalLocal.cpp    \
+    EffectHalLocal.cpp          \
+    EffectsFactoryHalLocal.cpp  \
+    StreamHalLocal.cpp
+
+else  # if !USE_LEGACY_LOCAL_AUDIO_HAL
 
 LOCAL_SRC_FILES := \
     ConversionHelperHidl.cpp   \
@@ -36,16 +47,7 @@
     android.hidl.memory@1.0                \
     libmedia_helper
 
-else  # if !ENABLE_TREBLE
-
-LOCAL_SRC_FILES := \
-    DeviceHalLocal.cpp          \
-    DevicesFactoryHalLocal.cpp  \
-    EffectBufferHalLocal.cpp    \
-    EffectHalLocal.cpp          \
-    EffectsFactoryHalLocal.cpp  \
-    StreamHalLocal.cpp
-endif  # ENABLE_TREBLE
+endif  # USE_LEGACY_LOCAL_AUDIO_HAL
 
 LOCAL_MODULE := libaudiohal