Expose default thread stack size set by chrome

This will be useful for stack sampling profiler to set buffer size
for copying stack.

BUG=859260

Change-Id: Ib87e44e82ff8d309e5ec2f7750fda9168b6906d0
Reviewed-on: https://chromium-review.googlesource.com/c/1297241Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: ssid <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603313}

base/threading/platform_thread.h

@@ -231,6 +231,10 @@ class BASE_EXPORT PlatformThread {
                                 ThreadPriority priority);
 #endif
 
+  // Returns the default thread stack size set by chrome. If we do not
+  // explicitly set default size then returns 0.
+  static size_t GetDefaultThreadStackSize();
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 };

base/threading/platform_thread_posix.cc

@@ -342,4 +342,11 @@ ThreadPriority PlatformThread::GetCurrentThreadPriority() {
 
 #endif  // !defined(OS_MACOSX) && !defined(OS_FUCHSIA)
 
+// static
+size_t PlatformThread::GetDefaultThreadStackSize() {
+  pthread_attr_t attributes;
+  pthread_attr_init(&attributes);
+  return base::GetDefaultThreadStackSize(attributes);
+}
+
 }  // namespace base

base/threading/platform_thread_unittest.cc

@@ -395,4 +395,16 @@ TEST(PlatformThreadTest, SetHugeThreadName) {
   PlatformThread::SetName(long_name);
 }
 
+TEST(PlatformThreadTest, GetDefaultThreadStackSize) {
+  size_t stack_size = PlatformThread::GetDefaultThreadStackSize();
+#if defined(OS_WIN) || defined(OS_IOS) || defined(OS_FUCHSIA) || \
+    (defined(OS_LINUX) && !defined(THREAD_SANITIZER)) ||         \
+    (defined(OS_ANDROID) && !defined(ADDRESS_SANITIZER))
+  EXPECT_EQ(0u, stack_size);
+#else
+  EXPECT_GT(stack_size, 0u);
+  EXPECT_LT(stack_size, 20u * (1 << 20));
+#endif
+}
+
 }  // namespace base

base/threading/platform_thread_win.cc

@@ -359,4 +359,9 @@ ThreadPriority PlatformThread::GetCurrentThreadPriority() {
   return ThreadPriority::NORMAL;
 }
 
+// static
+size_t PlatformThread::GetDefaultThreadStackSize() {
+  return 0;
+}
+
 }  // namespace base