Collect a single frame sample in the profiler if we can't validate stack boundaries

runtime/vm/profiler.h

 // Copyright (c) 2013, 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 VM_PROFILER_H_
 #define VM_PROFILER_H_
 
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
 #include "vm/code_observers.h"
@@ skipping 35 matching lines @@
   // following:
   //   * Accessing TLS -- Because on Windows the callback will be running in a
   //                      different thread.
   //   * Allocating memory -- Because this takes locks which may already be
   //                          held, resulting in a dead lock.
   //   * Taking a lock -- See above.
   static void SampleThread(Thread* thread,
                            const InterruptedThreadState& state);
 
  private:
+  // Does not walk the thread's stack.
+  static void SampleThreadSingleFrame(Thread* thread, uintptr_t pc);
   static bool initialized_;
 
   static SampleBuffer* sample_buffer_;
 
   friend class Thread;
 };
 
 
 class SampleVisitor : public ValueObject {
  public:
@@ skipping 585 matching lines @@
  private:
   ZoneGrowableArray<ProcessedSample*> samples_;
   CodeLookupTable* code_lookup_table_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessedSampleBuffer);
 };
 
 }  // namespace dart
 
 #endif  // VM_PROFILER_H_