[metrics] Add file output support

Adds a new command line option, -Xwrite-metrics-to-file=_, which
specifies a file for writing metrics to. This can be used in conjunction
with -Xwrite-metrics-to-log, which will cause the output to go to both
logcat and the file.

Writing metrics to a file can be helpful for testing or benchmarking
environments.

Access to the file is protected using advisory locking, so it is safe to
have multiple processes write metrics to the same file.

Test: test/run-test --host test/2234-write-metrics-to-file
Bug: 175025360, 170149255
Change-Id: I83a4f959cbb96847dc71188035c050a73b915064

1 files changed, 20 insertions, 0 deletions

diff --git a/test/2234-write-metrics-to-file/src/Main.java b/test/2234-write-metrics-to-file/src/Main.java
new file mode 100644
index 0000000000..0426192ab2
--- /dev/null
+++ b/test/2234-write-metrics-to-file/src/Main.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+public class Main {
+  public static void main(String[] args) {
+  }
+}