2c67cb17aa9c83a86e3882206ecf8ad5aeea49c9  <img>.width and .height are not density-corrected when the image is not being rendered

Classified as not security-relevant.
Triage note: Extracts naturalSize() and makes width()/height() (no-renderer path) and naturalWidth()/naturalHeight() share it via unclampedImageSizeForRenderer. Refactor unifying size computation; the null-image guard is preserved, no bug fixed.
This commit was flagged by the signal scorer and reviewed by AI (not a human). It is listed only so the triage is auditable; there is no root-cause analysis because this is not a vulnerability fix.

Structural signals: smartptr_member_added (+3.0), null_guard (+1.2), area:Source/WebCore/html (+2.0), surgical (+1.3)