Fix trailing whitespace in .cpp, .h, and .idl files

This fixes remaining trailing whitespace, following up:
Issue 20300002: Fix trailing whitespace in .cpp, .h, and .idl files (ex. Source/core)
https://codereview.chromium.org/20300002/

Done via:
sed -i -E 's/\s+$//' $(git ls-files -- '*.cpp' '*.h' '*.idl')

Per thread:
https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/yTZLvfbL8bQ/uXBlbHjUrOgJ

TBR=ojan, abarth

Review URL: https://codereview.chromium.org/20294002

git-svn-id: svn://svn.chromium.org/blink/trunk@154964 bbb929c8-8fbe-4397-9dbb-9b2b20218538