Autofill: Do not infer labels from divs with autofillable fields.

The label finding algorithm looks at previous divs to see if they contain text, and uses that text as the label. While this works for many webpages, not all webpages are structured this way. For a given field, when the neighbor divs contain input fields, they are likely not to be the label text.

BUG=454366

Review URL: https://codereview.chromium.org/906443002

Cr-Commit-Position: refs/heads/master@{#315688}
(cherry picked from commit 7db655c1268cca8f2e06eedb2e3ed7a0d01a9aeb)

Review URL: https://codereview.chromium.org/929393002

Cr-Commit-Position: refs/branch-heads/2272@{#310}
Cr-Branched-From: 827a380cfdb31aa54c8d56e63ce2c3fd8c3ba4d4-refs/heads/master@{#310958}

• chrome/test/data/autofill/heuristics/input/bug_454366.html[Added - diff]
• chrome/test/data/autofill/heuristics/output/bug_454366.out[Added - diff]
• components/autofill/content/renderer/form_autofill_util.cc[diff]