Fix trailing whitespace in .cpp, .h, and .idl files (ex. Source/core)

Done via script:
grep \
    --include='*.cpp' --include='*.h' --include='*.idl' \
    --exclude-dir='Source/core' \
    -r -l -E '\s+$' * |\
    xargs \
    sed -i -E -e 's/\s+$//'

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

TBR=abarth

Review URL: https://chromiumcodereview.appspot.com/20300002

git-svn-id: svn://svn.chromium.org/blink/trunk@154939 bbb929c8-8fbe-4397-9dbb-9b2b20218538