[base] Drop obsolete Thread::YieldCPU.

src/base/platform/platform-posix.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Platform-specific code for POSIX goes here. This is not a platform on its
 // own, but contains the parts which are the same across the POSIX platforms
 // Linux, MacOS, FreeBSD, OpenBSD, NetBSD and QNX.
 
 #include <errno.h>
 #include <limits.h>
@@ skipping 613 matching lines @@
   DCHECK(data_->thread_ != kNoThread);
   USE(result);
 }
 
 
 void Thread::Join() {
   pthread_join(data_->thread_, NULL);
 }
 
 
-void Thread::YieldCPU() {
-  int result = sched_yield();
-  DCHECK_EQ(0, result);
-  USE(result);
-}
-
-
 static Thread::LocalStorageKey PthreadKeyToLocalKey(pthread_key_t pthread_key) {
 #if V8_OS_CYGWIN
   // We need to cast pthread_key_t to Thread::LocalStorageKey in two steps
   // because pthread_key_t is a pointer type on Cygwin. This will probably not
   // work on 64-bit platforms, but Cygwin doesn't support 64-bit anyway.
   STATIC_ASSERT(sizeof(Thread::LocalStorageKey) == sizeof(pthread_key_t));
   intptr_t ptr_key = reinterpret_cast<intptr_t>(pthread_key);
   return static_cast<Thread::LocalStorageKey>(ptr_key);
 #else
   return static_cast<Thread::LocalStorageKey>(pthread_key);
@@ skipping 103 matching lines @@
 }
 
 
 void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
   pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
   int result = pthread_setspecific(pthread_key, value);
   DCHECK_EQ(0, result);
   USE(result);
 }
 
-
-} }  // namespace v8::base
+}  // namespace base
+}  // namespace v8