The TileController is failing to create margin tiles for the top and left sides when the there a scaled factor on the TileController that is less the 1.0.
Created attachment 224252 [details] Patch
Comment on attachment 224252 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=224252&action=review > Source/WebCore/platform/graphics/ca/mac/TileController.mm:474 > + topLeft.setX(floor((float)clampedRect.x() / leftMarginWidth())); floorf? > Source/WebCore/platform/graphics/ca/mac/TileController.mm:479 > + topLeft.setY(floor((float)clampedRect.y() / topMarginHeight())); Ditto.
floorf'd! Fixed with r164135