Merge branch 'master' into v4

Conflicts:
	Gruntfile.js
	dist/css/bootstrap-theme.css
	dist/css/bootstrap-theme.css.map
	dist/css/bootstrap-theme.min.css
	dist/css/bootstrap.css
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
	dist/js/bootstrap.min.js
	docs/_data/glyphicons.yml
	docs/_includes/components/alerts.html
	docs/_includes/components/badges.html
	docs/_includes/components/breadcrumbs.html
	docs/_includes/components/button-dropdowns.html
	docs/_includes/components/button-groups.html
	docs/_includes/components/dropdowns.html
	docs/_includes/components/glyphicons.html
	docs/_includes/components/input-groups.html
	docs/_includes/components/jumbotron.html
	docs/_includes/components/labels.html
	docs/_includes/components/list-group.html
	docs/_includes/components/media.html
	docs/_includes/components/navbar.html
	docs/_includes/components/navs.html
	docs/_includes/components/page-header.html
	docs/_includes/components/pagination.html
	docs/_includes/components/panels.html
	docs/_includes/components/progress-bars.html
	docs/_includes/components/responsive-embed.html
	docs/_includes/components/thumbnails.html
	docs/_includes/components/wells.html
	docs/_includes/css/buttons.html
	docs/_includes/css/code.html
	docs/_includes/css/forms.html
	docs/_includes/css/grid.html
	docs/_includes/css/helpers.html
	docs/_includes/css/images.html
	docs/_includes/css/less.html
	docs/_includes/css/tables.html
	docs/_includes/css/type.html
	docs/_includes/customizer-variables.html
	docs/_includes/getting-started/accessibility.html
	docs/_includes/getting-started/disabling-responsiveness.html
	docs/_includes/getting-started/download.html
	docs/_includes/getting-started/whats-included.html
	docs/_includes/js/alerts.html
	docs/_includes/js/buttons.html
	docs/_includes/js/carousel.html
	docs/_includes/js/collapse.html
	docs/_includes/js/modal.html
	docs/_includes/js/overview.html
	docs/_includes/js/popovers.html
	docs/_includes/js/tabs.html
	docs/_includes/js/tooltips.html
	docs/_includes/nav/components.html
	docs/_includes/nav/javascript.html
	docs/_jade/customizer-variables.jade
	docs/_layouts/default.html
	docs/about.html
	docs/assets/css/docs.min.css
	docs/assets/css/src/docs.css
	docs/assets/js/customize.min.js
	docs/assets/js/raw-files.min.js
	docs/assets/js/src/customizer.js
	docs/customize.html
	docs/dist/css/bootstrap-theme.css.map
	docs/dist/css/bootstrap.css
	docs/dist/css/bootstrap.css.map
	docs/dist/css/bootstrap.min.css
	less/glyphicons.less
	less/mixins/vendor-prefixes.less
	less/navbar.less
	less/popovers.less
	less/tables.less
	less/theme.less
	less/tooltip.less
	less/variables.less
	package.json
	scss/_carousel.scss
	scss/_close.scss
	scss/_forms.scss
	test-infra/npm-shrinkwrap.json

scss/_forms.scss

@@ -145,7 +145,7 @@ output {
   fieldset[disabled] & {
     cursor: $cursor-disabled;
     background-color: $input-bg-disabled;
-    opacity: 1; // iOS fix for unreadable disabled content
+    opacity: 1; // iOS fix for unreadable disabled content; see https://github.com/twbs/bootstrap/issues/11655
   }
 }
 
@@ -174,26 +174,24 @@ input[type="search"] {
 // In Mobile Safari, setting `display: block` on temporal inputs causes the
 // text within the input to become vertically misaligned. As a workaround, we
 // set a pixel line-height that matches the given height of the input, but only
-// for Safari.
+// for Safari. See https://bugs.webkit.org/show_bug.cgi?id=139848
 
 @media screen and (-webkit-min-device-pixel-ratio: 0) {
   input[type="date"],
   input[type="time"],
   input[type="datetime-local"],
   input[type="month"] {
-    line-height: $input-height-base;
-  }
-  input[type="date"].input-sm,
-  input[type="time"].input-sm,
-  input[type="datetime-local"].input-sm,
-  input[type="month"].input-sm {
-    line-height: $input-height-sm;
-  }
-  input[type="date"].input-lg,
-  input[type="time"].input-lg,
-  input[type="datetime-local"].input-lg,
-  input[type="month"].input-lg {
-    line-height: $input-height-lg;
+    line-height: @input-height-base;
+
+    &.input-sm,
+    .input-group-sm & {
+      line-height: @input-height-small;
+    }
+
+    &.input-lg,
+    .input-group-lg & {
+      line-height: @input-height-large;
+    }
   }
 }
 
@@ -460,8 +458,7 @@ input[type="checkbox"] {
     }
 
     // Remove default margin on radios/checkboxes that were used for stacking, and
-    // then undo the floating of radios and checkboxes to match (which also avoids
-    // a bug in WebKit: https://github.com/twbs/bootstrap/issues/1969).
+    // then undo the floating of radios and checkboxes to match.
     .radio,
     .checkbox {
       display: inline-block;