Record Chrome trace events in tcmalloc heap profiles

third_party/tcmalloc/chromium/src/stacktrace_x86-inl.h

 // Copyright (c) 2005, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 272 matching lines @@
 //   GetStack{Trace,Frames}WithContext()
 //
 // These functions take the following args:
 //   void** result: the stack-trace, as an array
 //   int* sizes: the size of each stack frame, as an array
 //               (GetStackFrames* only)
 //   int max_depth: the size of the result (and sizes) array(s)
 //   int skip_count: how many stack pointers to skip before storing in result
 //   void* ucp: a ucontext_t* (GetStack{Trace,Frames}WithContext only)
 
+//typedef int PseudoStackFunction(void** stack);
+//extern PseudoStackFunction* pseudo_stack_function;
+//int GET_STACK_TRACE_OR_FRAMES {
+//  int n = pseudo_stack_function(result);
+//#if IS_STACK_FRAMES
+//  // TODO(jamescook): Can we just skip this?
+//  memset(sizes, 0, n * sizeof(void*));  // Report unknown size.
+//#endif
+//  return n;
+//}
+
 int GET_STACK_TRACE_OR_FRAMES {
   void **sp;
 #if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 2) || __llvm__
   // __builtin_frame_address(0) can return the wrong address on gcc-4.1.0-k8.
   // It's always correct on llvm, and the techniques below aren't (in
   // particular, llvm-gcc will make a copy of pcs, so it's not in sp[2]),
   // so we also prefer __builtin_frame_address when running under llvm.
   sp = reinterpret_cast<void**>(__builtin_frame_address(0));
 #elif defined(__i386__)
   // Stack frame format:
@@ skipping 84 matching lines @@
           n++;
           continue;
         }
       }
       break;
     }
   }
 #endif  // KEEP_SHADOW_STACKS
   return n;
 }