Libcore: Expose whether app is native debuggable.

Bug: 27942453

(cherry picked from commit 0e28d3557851a7a17ca826501942bd26852c8287)

Change-Id: I3501749820b09945ce5422d3588581a05d668ebf
diff --git a/libart/src/main/java/dalvik/system/VMRuntime.java b/libart/src/main/java/dalvik/system/VMRuntime.java
index 8b27ca2..e53e103 100644
--- a/libart/src/main/java/dalvik/system/VMRuntime.java
+++ b/libart/src/main/java/dalvik/system/VMRuntime.java
@@ -288,6 +288,11 @@
     public native boolean isDebuggerActive();
 
     /**
+     * Returns true if native debugging is on.
+     */
+    public native boolean isNativeDebuggable();
+
+    /**
      * Registers a native allocation so that the heap knows about it and performs GC as required.
      * If the number of native allocated bytes exceeds the native allocation watermark, the
      * function requests a concurrent GC. If the native bytes allocated exceeds a second higher