Clean up template formatting errors and warts in build/scripts

This fixes 24 FIXMEs in the build/scripts templates:
all except for "replace call with filter".

The substantive changes (not just blank lines and removing {%-/-%}) are:
* StylePropertyShorthand.cpp.tmpl had an unnecessary test for length 1
  (can use a for loop even for length 1!)
* make_element_lookup_trie.py handled too much indentation itself
  (should be a template macro - added a FIXME - but anyway simplified)

Follow up to:
Simplify whitespace handling in build/ Jinja templates
https://codereview.chromium.org/236673002/
...which identified all these errors and warts.

R=abarth

Review URL: https://codereview.chromium.org/235943013

git-svn-id: svn://svn.chromium.org/blink/trunk@171556 bbb929c8-8fbe-4397-9dbb-9b2b20218538