Implement Harmony typography spec.

ui/views/controls/button/label_button.cc

Index: ui/views/controls/button/label_button.cc
diff --git a/ui/views/controls/button/label_button.cc b/ui/views/controls/button/label_button.cc
index 70a2f10e09b05d2748f2d52d9871398c35868586..f15aa17ea4863a2133beb3957795f0bd9780962c 100644
--- a/ui/views/controls/button/label_button.cc
+++ b/ui/views/controls/button/label_button.cc
@@ -238,6 +238,7 @@ gfx::Size LabelButton::GetPreferredSize() const {
 
   // Use a temporary label copy for sizing to avoid calculation side-effects.
   Label label(GetText(), {label_->font_list()});
+  label.SetLineHeight(label_->line_height());
   label.SetShadows(label_->shadows());
 
   if (style_ == STYLE_BUTTON && PlatformStyle::kDefaultLabelButtonHasBoldFont) {

[tapted, 2017/04/03 09:20:49]

This ButtonHasBoldFont thing is going away eventually... which will make the
whole temporary label thing unnecessary and make all the other traps obsolete.

But, since button subclasses or client code can call SetFontList() or
AdjustFontSize() on any Button (i.e. rather than just SetStyle) we can't switch
directly to having LabelButton pass STYLE_BUTTON through to the Label
constructor when it creates the button style. And although views::style *does*
give us a way to remove both SetFontList() and AdjustFontSize(), but that's
getting into chicken-and-egg territory.

So, for now, the SetLineHeight() call above is needed, even though the
typography spec returns `0` for button line heights. This is because
STYLE_PRIMARY calls for a line height under Harmony, and the calculations in
MdTextButton::UpdatePadding() will incorporate it, so if it's not _also_
incorporated here, then MD buttons will lose height and look wrong.