Fix a bunch of spelling mistakes :\

src/v8threads.h

 // Copyright 2008 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 81 matching lines @@
 // StartPreemption if there is more than one thread running. If not, a single
 // JavaScript can take full control of V8 and not allow other threads to run.
 class ContextSwitcher: public Thread {
  public:
   // Set the preemption interval for the ContextSwitcher thread.
   static void StartPreemption(int every_n_ms);
 
   // Stop sending preemption requests to threads.
   static void StopPreemption();
 
-  // Preempted thread needs to call back to the ContextSwitcher to acknowlege
+  // Preempted thread needs to call back to the ContextSwitcher to acknowledge
   // the handling of a preemption request.
   static void PreemptionReceived();
 
  private:
   explicit ContextSwitcher(int every_n_ms);
 
   void Run();
 
   bool keep_going_;
   int sleep_ms_;
 
   static ContextSwitcher* singleton_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_V8THREADS_H_