audio policy: add audio policy ready flag.

The audio policy ready flag indicates that audio policy manager
intialization is done and that audioflinger can call back
into audio policy service without risk of deadlocking because the
service is not published yet.

Bug: 188502620
Test: boot and kill native audioserver process.

Change-Id: I671ed0aadd0c51342be5b57d1afb7577da6a7fa9
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index eee1f2b..1ec2c96 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -574,6 +574,8 @@
                                 return INVALID_OPERATION;
                             }
 
+                product_strategy_t getStrategyForStream(audio_stream_type_t stream) const;
+
     virtual     void        dumpInternals_l(int fd __unused, const Vector<String16>& args __unused)
                             { }
     virtual     void        dumpTracks_l(int fd __unused, const Vector<String16>& args __unused) { }