Remove WebFrame::findChildByExpression.

This was used to find frames by xpath, but it has no remaining callers.

BUG=304341
TEST=no change

Review URL: https://codereview.chromium.org/215473002

git-svn-id: svn://svn.chromium.org/blink/trunk@170609 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Begin simplifying CompositedLayerMapping::updateAfterLayout

This CL unpacks the arguments to updateAfterLayout from being a bit field to
being separate Boolean values. As part of that unpacking, I learned that one of
the bits is always set, which let me remove an argument to
updateCompositingDescendantGeometry because it was always the same.

Review URL: https://codereview.chromium.org/220163006

git-svn-id: svn://svn.chromium.org/blink/trunk@170610 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Check for null selectors when looping in findBestRuleSetAndAdd.

This is necessary because a relation() of SubSelector does not in all cases guarantee that tagHistory() is non-NULL.

This happens in particular for this selector:

af|inputtext:focus::content { ... }

BUG=358475

Review URL: https://codereview.chromium.org/218403012

git-svn-id: svn://svn.chromium.org/blink/trunk@170611 bbb929c8-8fbe-4397-9dbb-9b2b20218538