Track async causal stack traces

runtime/vm/stack_trace.h

Index: runtime/vm/stack_trace.h
diff --git a/runtime/vm/stack_trace.h b/runtime/vm/stack_trace.h
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+++ b/runtime/vm/stack_trace.h
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+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef RUNTIME_VM_STACK_TRACE_H_
+#define RUNTIME_VM_STACK_TRACE_H_
+
+#include "vm/allocation.h"
+#include "vm/flag_list.h"
+#include "vm/object.h"
+
+namespace dart {
+
+DECLARE_FLAG(bool, show_invisible_frames);
+
+class StackTraceUtils : public AllStatic {
+ public:
+  /// Counts the number of stack frames.
+  /// Skips over the first |skip_frames|.
+  /// If |async_function| is not null, stops at the function that has
+  /// |async_function| as its parent.
+  static intptr_t CountFrames(
+      Thread* thread,
+      int skip_frames,
+      const Function& async_function,
+      bool count_invisible_frames = FLAG_show_invisible_frames);
+
+  /// Collects |count| frames into |code_array| and |pc_offset_array|.
+  /// Writing begins at |array_offset|.
+  /// Skips over the first |skip_frames|.
+  /// Returns the number of frames collected.
+  static intptr_t CollectFrames(
+      Thread* thread,
+      const Array& code_array,
+      const Array& pc_offset_array,
+      intptr_t array_offset,
+      intptr_t count,
+      int skip_frames,
+      bool collect_invisible_frames = FLAG_show_invisible_frames);
+
+  /// If |thread| has no async_stack_trace, does nothing.
+  /// Populates |async_function| with the top function of the async stack
+  /// trace. Populates |async_stack_trace|, |async_code_array|, and
+  /// |async_pc_offset_array| with the thread's async_stack_trace.
+  /// Returns the length of the asynchronous stack trace.
+  static intptr_t ExtractAsyncStackTraceInfo(Thread* thread,
+                                             Function* async_function,
+                                             StackTrace* async_stack_trace,
+                                             Array* async_code_array,
+                                             Array* async_pc_offset_array);
+};
+
+}  // namespace dart
+
+#endif  // RUNTIME_VM_STACK_TRACE_H_