Relanding "Multiprocess test client: Android child process launcher rework."

testing/android/native_test/java/src/org/chromium/native_test/MainRunner.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.native_test;
+
+import org.chromium.base.annotations.JNINamespace;
+
+/**
+ * This class provides a way to run the native main method.
+ * It is used in the multi-process test case, so that the child process can call
+ * the main method without //base/test:test_support's linkage requiring the
+ * main() symbol.
+ */
+@JNINamespace("testing::android")
+public final class MainRunner {
+    // Prevent instanciation.
+    private MainRunner() {
+    }
+
+    // Maps the file descriptors and executes the main method with the passed in command line.
+    public static int runMain(String[] commandLine, int[] fdsToMapKeys, int[] fdsToMapFds) {
+        return nativeRunMain(commandLine, fdsToMapKeys, fdsToMapFds);
+    }
+    private static native int nativeRunMain(
+            String[] commandLine, int[] fdsToMapKeys, int[] fdsToMapFds);
+}