clang-format: (WebKit) Disallow 1-line constructors with initializers.

Before:
  Constructor() : a(a) {}

After:
  Constructor()
      : a(a)
  {
  }

This style guide is pretty precise about this.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197980 91177308-0d34-0410-b5e6-96231b3b80d8