Windows: remove custom WindowsRunfiles impl.

Closes #6740.

PiperOrigin-RevId: 222543719
diff --git a/src/test/java/com/google/devtools/build/lib/windows/WindowsSubprocessTest.java b/src/test/java/com/google/devtools/build/lib/windows/WindowsSubprocessTest.java
index 3d13eff..4e4e120 100644
--- a/src/test/java/com/google/devtools/build/lib/windows/WindowsSubprocessTest.java
+++ b/src/test/java/com/google/devtools/build/lib/windows/WindowsSubprocessTest.java
@@ -21,11 +21,9 @@
 import com.google.devtools.build.lib.shell.SubprocessBuilder;
 import com.google.devtools.build.lib.testutil.TestSpec;
 import com.google.devtools.build.lib.util.OS;
-import com.google.devtools.build.lib.windows.util.WindowsTestUtil;
-
+import com.google.devtools.build.runfiles.Runfiles;
 import java.io.File;
 import java.nio.charset.Charset;
-
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -45,8 +43,10 @@
 
   @Before
   public void loadJni() throws Exception {
-    mockSubprocess = WindowsTestUtil.getRunfile(
-        "io_bazel/src/test/java/com/google/devtools/build/lib/MockSubprocess_deploy.jar");
+    Runfiles runfiles = Runfiles.create();
+    mockSubprocess =
+        runfiles.rlocation(
+            "io_bazel/src/test/java/com/google/devtools/build/lib/MockSubprocess_deploy.jar");
     mockBinary = System.getProperty("java.home") + "\\bin\\java.exe";
 
     process = null;