Collect array buffer allocation sizes for UMA in megabytes.

src/counters.h

Index: src/counters.h
diff --git a/src/counters.h b/src/counters.h
index e5e60fe5ade50727f92065a155a590fecfd57d00..6e619574abc7a577617c4fd330473f9f722e8a0e 100644
--- a/src/counters.h
+++ b/src/counters.h
@@ -929,8 +929,8 @@ class RuntimeCallTimerScope {
      51)                                                                      \
   HR(wasm_functions_per_wasm_module, V8.WasmFunctionsPerModule.wasm, 1,       \
      100000, 51)                                                              \
-  HR(array_buffer_big_allocations, V8.ArrayBufferBigAllocations, 1, 32, 32)   \
-  HR(array_buffer_new_size_failures, V8.ArrayBufferNewSizeFailures, 1, 32, 32)
+  HR(array_buffer_big_allocations, V8.ArrayBufferBigAllocations, 0, 4096, 13) \
+  HR(array_buffer_new_size_failures, V8.ArrayBufferNewSizeFailures, 0, 4096, 13)
 
 #define HISTOGRAM_TIMER_LIST(HT)                                               \
   /* Garbage collection timers. */                                             \