Track libcore.os' move to android.system.

(This is partial, but should cover everything in AOSP master except
for the zygote.)

Change-Id: I1042c99245765746a744c44e714095cb2c6cb75d
diff --git a/core/java/android/os/StatFs.java b/core/java/android/os/StatFs.java
index 9e9521a..13e9a15 100644
--- a/core/java/android/os/StatFs.java
+++ b/core/java/android/os/StatFs.java
@@ -16,9 +16,9 @@
 
 package android.os;
 
-import libcore.io.ErrnoException;
-import libcore.io.Libcore;
-import libcore.io.StructStatVfs;
+import android.system.ErrnoException;
+import android.system.Os;
+import android.system.StructStatVfs;
 
 /**
  * Retrieve overall information about the space on a filesystem. This is a
@@ -41,7 +41,7 @@
 
     private static StructStatVfs doStat(String path) {
         try {
-            return Libcore.os.statvfs(path);
+            return Os.statvfs(path);
         } catch (ErrnoException e) {
             throw new IllegalArgumentException("Invalid path: " + path, e);
         }