Add checks against incorrect context use in sysui tests

Fix incorrect usages found by this check.

Test: runtest systemui
Bug: 62251903
Change-Id: I45a762f96838e617833c1cbe003e583087bb8176
diff --git a/tests/testables/src/android/testing/ViewUtils.java b/tests/testables/src/android/testing/ViewUtils.java
index 5a651aa..fca44ae 100644
--- a/tests/testables/src/android/testing/ViewUtils.java
+++ b/tests/testables/src/android/testing/ViewUtils.java
@@ -31,12 +31,10 @@
                 LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT,
                 LayoutParams.TYPE_APPLICATION_OVERLAY,
                 0, PixelFormat.TRANSLUCENT);
-        InstrumentationRegistry.getContext()
-                .getSystemService(WindowManager.class).addView(view, lp);
+        view.getContext().getSystemService(WindowManager.class).addView(view, lp);
     }
 
     public static void detachView(View view) {
-        InstrumentationRegistry.getContext()
-                .getSystemService(WindowManager.class).removeViewImmediate(view);
+        view.getContext().getSystemService(WindowManager.class).removeViewImmediate(view);
     }
 }