Fill in StackSampler static functions for Android

There are existing POSIX implementations for these methods in
stack_sampler_posix.cc. We now use stack_sampler_android.cc on Android
and stack_sampler_posix.cc on all other POSIX platforms.

Note that there's an existing StackSamplerAndroid that exists in the
tracing namespace. However, that implementation is only used for the
"cpu_profiler" tracing category, whereas this implementation will be
used for stack sampled metrics. Once this new Android profiler is
sufficiently complete, it will also be used for tracing.
This stack_sampler_android.cc defers to StackSamplerImpl for its core
logic (also used by the Windows and Mac sampling profiler
implementations), whereas tracing's stack_sampler_android doesn't use
StackSamplerImpl and implements its own core logic.

R=wittman@chromium.org,gab@chromium.org

Bug: 988574
Change-Id: Ia1f20a22ac1421ff02d4beecff4beb6b7a0e065f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1727230Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Mike Wittman <wittman@chromium.org>
Commit-Queue: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682446}

base/BUILD.gn

@@ -626,6 +626,7 @@ jumbo_component("base") {
     "profiler/sample_metadata.h",
     "profiler/stack_sampler.cc",
     "profiler/stack_sampler.h",
+    "profiler/stack_sampler_android.cc",
     "profiler/stack_sampler_impl.cc",
     "profiler/stack_sampler_impl.h",
     "profiler/stack_sampler_mac.cc",
@@ -1331,7 +1332,10 @@ jumbo_component("base") {
 
   # Android.
   if (is_android) {
-    sources -= [ "debug/stack_trace_posix.cc" ]
+    sources -= [
+      "debug/stack_trace_posix.cc",
+      "profiler/stack_sampler_posix.cc",
+    ]
     sources += [
       "android/android_hardware_buffer_compat.cc",
       "android/android_hardware_buffer_compat.h",

base/profiler/stack_sampler_android.cc

+// Copyright 2019 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.
+
+#include "base/profiler/stack_sampler.h"
+
+#include <pthread.h>
+
+#include "base/profiler/native_unwinder_android.h"
+#include "base/profiler/stack_sampler_impl.h"
+#include "base/profiler/thread_delegate_android.h"
+#include "base/threading/platform_thread.h"
+
+namespace base {
+
+std::unique_ptr<StackSampler> StackSampler::Create(
+    PlatformThreadId thread_id,
+    ModuleCache* module_cache,
+    StackSamplerTestDelegate* test_delegate) {
+  return std::make_unique<StackSamplerImpl>(
+      std::make_unique<ThreadDelegateAndroid>(),
+      std::make_unique<NativeUnwinderAndroid>(), module_cache, test_delegate);
+}
+
+size_t StackSampler::GetStackBufferSize() {
+  size_t stack_size = PlatformThread::GetDefaultThreadStackSize();
+
+  pthread_attr_t attr;
+  if (stack_size == 0 && pthread_attr_init(&attr) == 0) {
+    if (pthread_attr_getstacksize(&attr, &stack_size) != 0)
+      stack_size = 0;
+    pthread_attr_destroy(&attr);
+  }
+
+  // 1MB is default thread limit set by Android at art/runtime/thread_pool.h.
+  constexpr size_t kDefaultStackLimit = 1 << 20;
+  return stack_size > 0 ? stack_size : kDefaultStackLimit;
+}
+
+}  // namespace base

base/profiler/stack_sampler_posix.cc

@@ -28,14 +28,8 @@ size_t StackSampler::GetStackBufferSize() {
     pthread_attr_destroy(&attr);
   }
 
-// If we can't get stack limit from pthreads then use default value.
-#if defined(OS_ANDROID)
-  // 1MB is default thread limit set by Android at art/runtime/thread_pool.h.
-  constexpr size_t kDefaultStackLimit = 1 << 20;
-#else
   // Maximum limits under NPTL implementation.
   constexpr size_t kDefaultStackLimit = 4 * (1 << 20);
-#endif
   return stack_size > 0 ? stack_size : kDefaultStackLimit;
 }