Remove workaround for borked sem_init library function.

This workaround had been added because sanitizer interceptors were
linking against an old version of GLIBC. The respective sanitizers
within LLVM have by now be fixed, workaround can be removed.

The original workaround: https://codereview.chromium.org/1407463002

R=machenbach@chromium.org
BUG=chromium:536813

Review-Url: https://codereview.chromium.org/2045993003
Cr-Commit-Position: refs/heads/master@{#36816}

src/base/platform/semaphore.cc

@@ -87,10 +87,6 @@ Semaphore::Semaphore(int count) {
       0, reinterpret_cast<uintptr_t>(&native_handle_) &
       kSemaphoreAlignmentMask);
   DCHECK(count >= 0);
-#if V8_LIBC_GLIBC
-  // sem_init in glibc prior to 2.1 does not zero out semaphores.
-  memset(&native_handle_, 0, sizeof(native_handle_));
-#endif
   int result = sem_init(&native_handle_, 0, count);
   DCHECK_EQ(0, result);
   USE(result);