Add Mic Toggle button to AppRTCDemo (Android).

webrtc/examples/androidapp/res/layout/fragment_call.xml

Index: webrtc/examples/androidapp/res/layout/fragment_call.xml
diff --git a/webrtc/examples/androidapp/res/layout/fragment_call.xml b/webrtc/examples/androidapp/res/layout/fragment_call.xml
index 5d71d73f50d4328ca1937b44bba756a133d1dcea..26c289e91aa90fced901e8110121feb7747a40c7 100644
--- a/webrtc/examples/androidapp/res/layout/fragment_call.xml
+++ b/webrtc/examples/androidapp/res/layout/fragment_call.xml
@@ -47,6 +47,14 @@
            android:contentDescription="@string/disconnect_call"
            android:layout_width="48dp"
            android:layout_height="48dp"/>
+
+       <ImageButton
+           android:id="@+id/button_call_toggle_mic"
+           android:background="@android:drawable/ic_btn_speak_now"
+           android:contentDescription="@string/switch_camera"

[AlexG, 2016/03/22 16:49:20]

nit: Add new content description string for mic mute button instead of
"switch_camera"?

[the sun, 2016/03/23 08:25:44]

Oops, thanks. Done.

+           android:layout_marginEnd="8dp"
+           android:layout_width="48dp"
+           android:layout_height="48dp"/>
     </LinearLayout>
 
     <TextView