Collect array buffer allocation sizes for UMA in megabytes.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 2901840af92fbe0b1cd995ba1129a4cb4024befa..957fe771b4a020bbeb08e477a68acacedc0b117e 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -19463,6 +19463,13 @@ void JSArrayBuffer::Setup(Handle<JSArrayBuffer> array_buffer, Isolate* isolate,
   }
 }
 
+namespace {
+
+inline int convertToMb(size_t size) {

[bbudge, 2017/04/03 23:11:40]

nit: ConvertToMb (first letter upper case for free function.)

[kschimpf, 2017/04/04 17:00:01]

Done.

+  return static_cast<int>(size / static_cast<size_t>(MB));
+}
+
+}  // namespace
 
 bool JSArrayBuffer::SetupAllocatingData(Handle<JSArrayBuffer> array_buffer,
                                         Isolate* isolate,
@@ -19473,12 +19480,8 @@ bool JSArrayBuffer::SetupAllocatingData(Handle<JSArrayBuffer> array_buffer,
   // Prevent creating array buffers when serializing.
   DCHECK(!isolate->serializer_enabled());
   if (allocated_length != 0) {
-    constexpr size_t kMinBigAllocation = 1 << 20;
-    if (allocated_length >= kMinBigAllocation) {
-      isolate->counters()->array_buffer_big_allocations()->AddSample(
-          sizeof(uint64_t) * kBitsPerByte -
-          base::bits::CountLeadingZeros64(allocated_length));
-    }
+    isolate->counters()->array_buffer_big_allocations()->AddSample(
+        convertToMb(allocated_length));
     if (initialize) {
       data = isolate->array_buffer_allocator()->Allocate(allocated_length);
     } else {
@@ -19487,8 +19490,7 @@ bool JSArrayBuffer::SetupAllocatingData(Handle<JSArrayBuffer> array_buffer,
     }
     if (data == NULL) {
       isolate->counters()->array_buffer_new_size_failures()->AddSample(
-          sizeof(uint64_t) * kBitsPerByte -
-          base::bits::CountLeadingZeros64(allocated_length));
+          convertToMb(allocated_length));
       return false;
     }
   } else {