Android: Add helper methods for printing native stack traces

This CL adds utility functions to unwind the stack for a given thread on
Android ARM devices. This works on top of unwind.h and unwinds native
(C++) stack traces only. Unwinding a thread from another thread is done
by overriding the signal handler with a custom function and then
interrupting the specific thread.

Bug: webrtc:10168
Change-Id: If5adffd3a6bb57bf502168743e09a7eefc292bf3
Reviewed-on: https://webrtc-review.googlesource.com/c/118141
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26328}

sdk/android/native_api/stacktrace/stacktrace.h

@@ -0,0 +1,42 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef SDK_ANDROID_NATIVE_API_STACKTRACE_STACKTRACE_H_
+#define SDK_ANDROID_NATIVE_API_STACKTRACE_STACKTRACE_H_
+
+#include <string>
+#include <vector>
+
+namespace webrtc {
+
+struct StackTraceElement {
+  // Pathname of shared object (.so file) that contains address.
+  const char* shared_object_path;
+  // Execution address relative to the .so base address. This matches the
+  // addresses you get with "nm", "objdump", and "ndk-stack", as long as the
+  // code is compiled with position-independent code. Android requires
+  // position-independent code since Lollipop.
+  uint32_t relative_address;
+  // Name of symbol whose definition overlaps the address. This value is null
+  // when symbol names are stripped.
+  const char* symbol_name;
+};
+
+// Utility to unwind stack for a given thread on Android ARM devices. This works
+// on top of unwind.h and unwinds native (C++) stack traces only.
+std::vector<StackTraceElement> GetStackTrace(int tid);
+
+// Get a string representation of the stack trace in a format ndk-stack accepts.
+std::string StackTraceToString(
+    const std::vector<StackTraceElement>& stack_trace);
+
+}  // namespace webrtc
+
+#endif  // SDK_ANDROID_NATIVE_API_STACKTRACE_STACKTRACE_H_