Remove disableBackgroundScheduling.

This function is a no-oop.

It is made private for now since it is still referenced by
one device's prebuilts.

Bug: 66905301
Test: m
Change-Id: Ibf5b34b0c07decd4a7676caa4d4011ea824d0679
diff --git a/IPCThreadState.cpp b/IPCThreadState.cpp
index 1481967..f6536f6 100644
--- a/IPCThreadState.cpp
+++ b/IPCThreadState.cpp
@@ -275,7 +275,6 @@
 static bool gHaveTLS = false;
 static pthread_key_t gTLS = 0;
 static bool gShutdown = false;
-static bool gDisableBackgroundScheduling = false;
 
 IPCThreadState* IPCThreadState::self()
 {
@@ -333,10 +332,8 @@
     }
 }
 
-void IPCThreadState::disableBackgroundScheduling(bool disable)
-{
-    gDisableBackgroundScheduling = disable;
-}
+// TODO(b/66905301): remove symbol
+void IPCThreadState::disableBackgroundScheduling(bool /* disable */) {}
 
 sp<ProcessState> IPCThreadState::process()
 {