Add initialization for has_external_callback field.

tools/tickprocessor.js

 // Copyright 2009 the V8 project authors. 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 327 matching lines @@
     this.deserializedEntriesNames_[addr] =
       this.snapshotLogProcessor_.getSerializedEntryName(pos);
   }
 };
 
 
 TickProcessor.prototype.includeTick = function(vmState) {
   return this.stateFilter_ == null || this.stateFilter_ == vmState;
 };
 
-
 TickProcessor.prototype.processTick = function(pc,
                                                sp,
                                                is_external_callback,
                                                tos_or_external_callback,
                                                vmState,
                                                stack) {
   this.ticks_.total++;
   if (vmState == TickProcessor.VmStates.GC) this.ticks_.gc++;
   if (!this.includeTick(vmState)) {
     this.ticks_.excluded++;
     return;
   }
   if (is_external_callback) {
     // Don't use PC when in external callback code, as it can point
     // inside callback's code, and we will erroneously report
-    // that a callback calls itself.
-    pc = 0;
+    // that a callback calls itself. Instead we use tos_or_external_callback,
+    // as simply resetting PC will produce unaccounted ticks.
+    pc = tos_or_external_callback;
+    tos_or_external_callback = 0;
   } else if (tos_or_external_callback) {
     // Find out, if top of stack was pointing inside a JS function
     // meaning that we have encountered a frameless invocation.
     var funcEntry = this.profile_.findEntry(tos_or_external_callback);
     if (!funcEntry || !funcEntry.isJSFunction || !funcEntry.isJSFunction()) {
       tos_or_external_callback = 0;
     }
   }
 
   this.profile_.recordTick(this.processStack(pc, tos_or_external_callback, stack));
@@ skipping 491 matching lines @@
       if (arg !== synArg && dispatch === this.argsDispatch_[synArg]) {
         synonims.push(synArg);
         delete this.argsDispatch_[synArg];
       }
     }
     print('  ' + padRight(synonims.join(', '), 20) + dispatch[2]);
   }
   quit(2);
 };