There should never be unplaced floats from other blocks.

When positioning new floats in a block, all unplaced floats should belong to
said block. If we find unplaced floats from other blocks, someone somewhere
must have forgotten to place them on their own.

No need for code to skip such floats. DCHECK instead.

Review-Url: https://codereview.chromium.org/2479173002
Cr-Commit-Position: refs/heads/master@{#430544}
1 file changed