Expose defaultContentEdgeInsets readonly property on MDCButton in r…

…egular header for the class, rather than only in the subclassing header, as clients may need to reset content insets back to their defaults after using a themer, even if they do not subclass MDCButton.

PiperOrigin-RevId: 316165414

components/Buttons/src/MDCButton.h

@@ -90,6 +90,11 @@
 */
 @property(nonatomic, assign) UIEdgeInsets visibleAreaInsets;
 
+/**
+ The default content edge insets of the button. They are set at initialization time.
+ */
+@property(nonatomic, readonly) UIEdgeInsets defaultContentEdgeInsets;
+
 /**
  The offset (in points) of the button's inkView or rippleView (depending on which is being used -
  see @c enableRippleBehavior)

components/Buttons/src/private/MDCButton+Subclassing.h

@@ -37,7 +37,4 @@
 /** The bounding path of the button. The shadow will follow that path. */
 - (nonnull UIBezierPath *)boundingPath;
 
-/** The default content edge insets of the button. They are set at initialization time. */
-- (UIEdgeInsets)defaultContentEdgeInsets;
-
 @end