Delete RenderBoxModelObject::layerTypeRequired.

Only RenderBox and RenderInline inherit from RenderBoxModelObject
and both of those override layerTypeRequired, so this is
dead code.

Review URL: https://codereview.chromium.org/227683010

git-svn-id: svn://svn.chromium.org/blink/trunk@171018 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: Clean up a way use_in_heap_object is used in the IDL compiler

This is a preparation CL for supporting a [GarbageCollected] IDL attribute.

- This CL renames use_in_heap_object to in_array_or_sequence, which indicates whether the C++ type is used in an array or sequence.

- This CL cleans up how in_array_or_sequence is used.

- There is no change in generated code.

BUG=340522

Review URL: https://codereview.chromium.org/227373008

git-svn-id: svn://svn.chromium.org/blink/trunk@171019 bbb929c8-8fbe-4397-9dbb-9b2b20218538