Set read file permissions for WM trace

Test: Flash a device. Enable WM trace. Disable WM trace. Check
/data/misc/wmtrace for the read permissions for wm_trace.pb

Change-Id: Ib5cb7cd825b167156fe1dd5ab62dc99a2a811bdc

services/core/java/com/android/server/wm/WindowTraceBuffer.java

@@ -93,8 +93,8 @@ class WindowTraceBuffer {
     void writeTraceToFile(File traceFile) throws IOException {
         synchronized (mBufferLock) {
             traceFile.delete();
-            traceFile.setReadable(true, false);
             try (OutputStream os = new FileOutputStream(traceFile)) {
+                traceFile.setReadable(true /* readable */, false /* ownerOnly */);
                 ProtoOutputStream proto = new ProtoOutputStream();
                 proto.write(MAGIC_NUMBER, MAGIC_NUMBER_VALUE);
                 os.write(proto.getBytes());