Merge branch 'v4-dev' of https://github.com/twbs/bootstrap into v4-dev

docs/utilities/responsive-helpers.md

@@ -14,7 +14,7 @@ Rules are directly applied to `<iframe>`, `<embed>`, `<video>`, and `<object>` e
 
 {% example html %}
 <div class="embed-responsive embed-responsive-16by9">
-  <iframe class="embed-responsive-item" src="//www.youtube.com/embed/zpOULjyy-n8?rel=0" allowfullscreen></iframe>
+  <iframe class="embed-responsive-item" src="https://www.youtube.com/embed/zpOULjyy-n8?rel=0" allowfullscreen></iframe>
 </div>
 {% endexample %}
 

scss/_breadcrumb.scss

 .breadcrumb {
   padding: $breadcrumb-padding-y $breadcrumb-padding-x;
-  margin-bottom: $spacer-y;
+  margin-bottom: 1rem;
   list-style: none;
   background-color: $breadcrumb-bg;
   @include border-radius($border-radius);

scss/_images.scss

@@ -33,7 +33,7 @@
 }
 
 .figure-img {
-  margin-bottom: ($spacer-y / 2);
+  margin-bottom: ($spacer / 2);
   line-height: 1;
 }
 

scss/mixins/_box-shadow.scss

+@mixin box-shadow($shadow...) {
+  @if $enable-shadows {
+    box-shadow: $shadow;
+  }
+}

scss/mixins/_nav-divider.scss

@@ -4,7 +4,7 @@
 
 @mixin nav-divider($color: #e5e5e5) {
   height: 1px;
-  margin: ($spacer-y / 2) 0;
+  margin: ($spacer / 2) 0;
   overflow: hidden;
   background-color: $color;
 }

scss/mixins/_transition.scss

+@mixin transition($transition...) {
+  @if $enable-transitions {
+    @if length($transition) == 0 {
+      transition: $transition-base;
+    } @else {
+      transition: $transition;
+    }
+  }
+}

scss/mixins/_visibility.scss

 // Visibility
 
-@mixin invisible {
-  visibility: hidden !important;
+@mixin invisible($visibility) {
+  visibility: $visibility !important;
 }