In revision r16122, all spaces in editable text nodes were changed to be non-breaking spaces instead of space/non-breaking space pairs as necessary. However, RenderText calculates its min/max widths assuming that non-breaking spaces cannot be broken independent of -webkit-nbsp-mode. This causes a problem when a contentEditable div is absolutely positioned to the right, then as text is typed into the div, once the amount of text inserted is longer than one line, there will be a run of characters which RenderText thinks cannot be broken, and so the width of the editable div will increase.
Created attachment 11479 [details]
I don't really like the huge number of editing delegate messages generated by the layout test for this bug, but I couldn't reproduce the bug by replacing the typeCharacterCommand()'s by a single document.execCommand('InsertText', ...).
All other layout tests pass.
Created attachment 11480 [details]
Testcase no longer uses editing code, and hence has been moved to fast/text/whitespace/nbsp-mode-and-linewraps.html.
Comment on attachment 11480 [details]
Committed in r17724.
Comment on attachment 11479 [details]
RenderStyle is not an appropriate spot for an isSpace helper like this.
Created attachment 11482 [details]
Follow patch to remove the helper function from RenderStyle
Comment on attachment 11482 [details]