Try to rename LayoutDistanceType enum values for clarity and consistency.

BUTTON_[H,V]EDGE_MARGIN_NEW -> DIALOG_BUTTON_MARGIN
Combined these two (which are the same in both pre-Harmony and Harmony) into
one.  Eliminated NEW (was unfortunate even in the original pre-Harmony name and
is especially misleading now).  Tried to choose a naming structure for
parallelism with PANEL_CONTENT_MARGIN (see below): the dialog-scope margin
around buttons.

CHECKBOX_INDENT -> SUBSECTION_HORIZONTAL_INDENT
Added HORIZONTAL to match other names that are specific to horizontal vs
vertical.  Changed to SUBSECTION based on
https://codereview.chromium.org/2654123004/ .

PANEL_[HORIZ,VERT]_MARGIN -> PANEL_CONTENT_MARGIN
Again, combined two always-the same constants into one.

UNRELATED_CONTROL_LARGE_VERTICAL_SPACING ->
UNRELATED_CONTROL_VERTICAL_SPACING_LARGE
Moved "large" to the end so this would sort alphabetically by the non-LARGE
version.

I also sorted the declarations/switch statements for these into alphabetical
order, and tried to improve some comments.

In a future cleanup, I'd like to change existing uses of the old layout
constants to these values (which wiill help with Harmonization in general) and
then remove the old constants, which will eliminate things like name mismatches
between the old and new names.

BUG=none
TEST=none

Review-Url: https://codereview.chromium.org/2666043002
Cr-Commit-Position: refs/heads/master@{#447425}
7 files changed