small misspelling fixes.

src/heap.h

 // Copyright 2012 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 701 matching lines @@
 
   MUST_USE_RESULT MaybeObject* AllocateJSFunctionProxy(Object* handler,
                                                        Object* call_trap,
                                                        Object* construct_trap,
                                                        Object* prototype);
 
   // Reinitialize a JSReceiver into an (empty) JS object of respective type and
   // size, but keeping the original prototype.  The receiver must have at least
   // the size of the new object.  The object is reinitialized and behaves as an
   // object that has been freshly allocated.
-  // Returns failure if an error occured, otherwise object.
+  // Returns failure if an error occurred, otherwise object.
   MUST_USE_RESULT MaybeObject* ReinitializeJSReceiver(JSReceiver* object,
                                                       InstanceType type,
                                                       int size);
 
   // Reinitialize an JSGlobalProxy based on a constructor.  The object
   // must have the same size as objects allocated using the
   // constructor.  The object is reinitialized and behaves as an
   // object that has been freshly allocated using the constructor.
   MUST_USE_RESULT MaybeObject* ReinitializeJSGlobalProxy(
       JSFunction* constructor, JSGlobalProxy* global);
@@ skipping 2329 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_