Issue 7016: Auto-completion of global/local variables doesn't work when stopped in debugger

https://code.google.com/p/fbug/issues/detail?id=7016
Be more cautious when extracting names from the same line in auto-completion

In particular, "cd(frames[0])" should not offer "cd" as the name of a
new global. Related to issue 6206.
Remove some dead Chromebug code