Some optimizations for the array alloc path.

- Force Array::Alloc() to be inlined.
- Simplify the array size overflow check.
- Turn fill_usable into a template parameter.
- Remove a branch in Array::DataOffset() and avoid
  Primitive::ComponentSize(), which has a switch, in the array alloc
  path.
- Strength reductions in the array size computation by using component
  size shifts instead of component sizes. Store component size shift
  in the upper 16 bits of primitive_type field.
- Speedup: ~4% (3435->3284) in MemAllocTest on N4.

Bug: 9986565

Change-Id: I4b142ffac4ab8b5b915836f1660a949d6442344c
diff --git a/runtime/mirror/array.cc b/runtime/mirror/array.cc
index 4535f6c..636be33 100644
--- a/runtime/mirror/array.cc
+++ b/runtime/mirror/array.cc
@@ -48,7 +48,8 @@
   StackHandleScope<1> hs(self);
   Handle<Array> new_array(
       hs.NewHandle(
-          Array::Alloc<true>(self, array_class.Get(), array_length, array_class->GetComponentSize(),
+          Array::Alloc<true>(self, array_class.Get(), array_length,
+                             array_class->GetComponentSizeShift(),
                              Runtime::Current()->GetHeap()->GetCurrentAllocator())));
   if (UNLIKELY(new_array.Get() == nullptr)) {
     CHECK(self->IsExceptionPending());