Add V8 shared array allocation sizes histogram.

src/counters.h

Index: src/counters.h
diff --git a/src/counters.h b/src/counters.h
index b07381463faebc0579ce3b9dda780ba1543914cf..38f5446eabf4d48359dad5a69e4ab12f313d91c1 100644
--- a/src/counters.h
+++ b/src/counters.h
@@ -978,7 +978,9 @@ class RuntimeCallTimerScope {
      100000, 51)                                                              \
   HR(array_buffer_big_allocations, V8.ArrayBufferLargeAllocations, 0, 4096,   \
      13)                                                                      \
-  HR(array_buffer_new_size_failures, V8.ArrayBufferNewSizeFailures, 0, 4096, 13)
+  HR(array_buffer_new_size_failures, V8.ArrayBufferNewSizeFailures, 0, 4096,  \
+     13)                                                                      \
+  HR(shared_array_allocations, V8.SharedArrayAllocationSizes, 0, 4096, 13)
 
 #define HISTOGRAM_TIMER_LIST(HT)                                               \
   /* Garbage collection timers. */                                             \