Revert^2 "Remove VMRuntime.concurrentGC"

548136c7a3c98edaf0f325671a23dc7150315d13

Change-Id: Ie325a2e258e744dc0411b225e78fa6c7ed2aed08
diff --git a/libart/src/main/java/dalvik/system/VMRuntime.java b/libart/src/main/java/dalvik/system/VMRuntime.java
index 068c352..20f9538 100644
--- a/libart/src/main/java/dalvik/system/VMRuntime.java
+++ b/libart/src/main/java/dalvik/system/VMRuntime.java
@@ -631,7 +631,6 @@
     @libcore.api.CorePlatformApi
     public native void requestConcurrentGC();
 
-    public native void concurrentGC();
     public native void requestHeapTrim();
     public native void trimHeap();
     public native void startHeapTaskProcessor();