Revert 126020 - Experiment for updating the tcmalloc chromium branch to r144 (gperftools 2.0).

third_party/tcmalloc/chromium/src/base/spinlock_internal.cc

Index: third_party/tcmalloc/chromium/src/base/spinlock_internal.cc
===================================================================
--- third_party/tcmalloc/chromium/src/base/spinlock_internal.cc	(revision 126022)
+++ third_party/tcmalloc/chromium/src/base/spinlock_internal.cc	(working copy)
@@ -42,9 +42,6 @@
 
 #include "base/spinlock_internal.h"
 
-// forward declaration for use by spinlock_*-inl.h
-namespace base { namespace internal { static int SuggestedDelayNS(int loop); }}
-
 #if defined(_WIN32)
 #include "base/spinlock_win32-inl.h"
 #elif defined(__linux__)
@@ -76,27 +73,5 @@
   return v;
 }
 
-// Return a suggested delay in nanoseconds for iteration number "loop"
-static int SuggestedDelayNS(int loop) {
-  // Weak pseudo-random number generator to get some spread between threads
-  // when many are spinning.
-  static base::subtle::Atomic64 rand;
-  uint64 r = base::subtle::NoBarrier_Load(&rand);
-  r = 0x5deece66dLL * r + 0xb;   // numbers from nrand48()
-  base::subtle::NoBarrier_Store(&rand, r);
-
-  r <<= 16;   // 48-bit random number now in top 48-bits.
-  if (loop < 0 || loop > 32) {   // limit loop to 0..32
-    loop = 32;
-  }
-  // loop>>3 cannot exceed 4 because loop cannot exceed 32.
-  // Select top 20..24 bits of lower 48 bits,
-  // giving approximately 0ms to 16ms.
-  // Mean is exponential in loop for first 32 iterations, then 8ms.
-  // The futex path multiplies this by 16, since we expect explicit wakeups
-  // almost always on that path.
-  return r >> (44 - (loop >> 3));
-}
-
 } // namespace internal
 } // namespace base