Composited Layers that contain only an Image follow a special path that doesn't require allocating additional storage for keeping around the associated bitmap. That path hasn't been implemented in LayerChromium yet.
Created attachment 56121 [details] Proposed patch
Comment on attachment 56121 [details] Proposed patch WebCore/ChangeLog:6 + an Image element. nit: please add a bug reference here. R=me with that fixed.
Created attachment 56124 [details] Patch fixed. Added URL to bug in ChangeLog
Uploaded the fix but I'm afraid that I might have inadvertently overwrite the r+ bit..
Comment on attachment 56124 [details] Patch fixed. Added URL to bug in ChangeLog Clearing flags on attachment: 56124 Committed r59550: <http://trac.webkit.org/changeset/59550>
All reviewed patches have been landed. Closing bug.