Don't use return_type macro on base initial methods in ComputedStyle.

There is a Jinja macro called return_type that takes a field, and
returns the ref version of field.type_name if the field is not a
bitfield. However, this macro is being used as the return type for
initial methods like InitialWidth(). This is is bad because if the
field is not a bitfield, then we would generate some code like:

static const Width& InitialPosition() {
   return Length();
}

instead of the correct:

static Width InitialPosition() {
   return Length();
}

BUG=628043

Review-Url: https://codereview.chromium.org/2830973002
Cr-Commit-Position: refs/heads/master@{#465871}
1 file changed