Pull out commandToString() from FastMixerDumpState.cpp

to FastThreadState.cpp, FastMixerState.cpp, and FastCaptureState.cpp

Change-Id: I872efb211e8a0335c42906367859d3674340e374
diff --git a/services/audioflinger/FastMixerState.cpp b/services/audioflinger/FastMixerState.cpp
index 3aa8dad..a8c2634 100644
--- a/services/audioflinger/FastMixerState.cpp
+++ b/services/audioflinger/FastMixerState.cpp
@@ -39,4 +39,19 @@
 {
 }
 
+// static
+const char *FastMixerState::commandToString(Command command)
+{
+    const char *str = FastThreadState::commandToString(command);
+    if (str != NULL) {
+        return str;
+    }
+    switch (command) {
+    case FastMixerState::MIX:       return "MIX";
+    case FastMixerState::WRITE:     return "WRITE";
+    case FastMixerState::MIX_WRITE: return "MIX_WRITE";
+    }
+    LOG_ALWAYS_FATAL("%s", __func__);
+}
+
 }   // namespace android