Rename Visualizer::mLock

This avoids confusion with parent class AudioEffect's mLock which is
protected.

Change-Id: I2ae0b0869fe3c606f682252973795b34477951d0
diff --git a/include/media/Visualizer.h b/include/media/Visualizer.h
index 5d2c874..1a4cbca 100644
--- a/include/media/Visualizer.h
+++ b/include/media/Visualizer.h
@@ -143,7 +143,7 @@
     void periodicCapture();
     uint32_t initCaptureSize();
 
-    Mutex mLock;
+    Mutex mCaptureLock;
     uint32_t mCaptureRate;
     uint32_t mCaptureSize;
     uint32_t mSampleRate;