introduce a background-hang-monitor:

Mac-Os implementation of a thread sampler,
Linux and Windows skeleton implementations.

components/background_hang_monitor/lib.rs

@@ -0,0 +1,21 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![deny(unsafe_code)]
+
+#[macro_use]
+extern crate crossbeam_channel;
+#[macro_use]
+extern crate log;
+
+pub mod background_hang_monitor;
+mod sampler;
+#[cfg(any(target_os = "android", target_os = "linux"))]
+mod sampler_linux;
+#[cfg(target_os = "macos")]
+mod sampler_mac;
+#[cfg(target_os = "windows")]
+mod sampler_windows;
+
+pub use self::background_hang_monitor::*;