[cleanup] Properly order the fields and accessors in JSArrayBuffer.

kByteLengthOffset is actually at the start of the object, so to avoid
confusion, put the accessor declarations in the same order as the
actual fields.

Change-Id: Ic92e597911235ccf126cf934151a0886e5d2a6f6
Reviewed-on: https://chromium-review.googlesource.com/725325Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48686}

src/objects/js-array.h

@@ -134,12 +134,12 @@ enum class SharedFlag { kNotShared, kShared };
 
 class JSArrayBuffer : public JSObject {
  public:
-  // [backing_store]: backing memory for this array
-  DECL_ACCESSORS(backing_store, void)
-
   // [byte_length]: length in bytes
   DECL_ACCESSORS(byte_length, Object)
 
+  // [backing_store]: backing memory for this array
+  DECL_ACCESSORS(backing_store, void)
+
   // [allocation_base]: the start of the memory allocation for this array,
   // normally equal to backing_store
   DECL_ACCESSORS(allocation_base, void)