For text blocks that are just whitespace and stripFrontSpaces=true, when checking if the block should be considered for breaking, beginWS and endWS are used, but are uninitialized (RenderBlock.cpp:3741).
They don't get initialized in RenderText::trimmedPrefWidths() since it returns early.
I'm not sure if such blocks should be considered for breaking, so I don't know what values to initialize beginWS and endWS to.
Confirming. This is a regression from newly-added code.
Created attachment 16009 [details]
All-whitespace text test case
I think the code in RenderBlock::calcInlinePrefWidths is wrong anyway as demonstrated by this test case.
What kind of effects could we see on real-world sites from this bug?
*** Bug 16414 has been marked as a duplicate of this bug. ***
*** Bug 19083 has been marked as a duplicate of this bug. ***
*** Bug 20194 has been marked as a duplicate of this bug. ***
Created attachment 22959 [details]
Fixed in <http://trac.webkit.org/changeset/35902>.