Core: Remove IE-specific support tests, rely on document.documentMode

Also, update some tests to IE-sniff when deciding whether
to skip a test.

Fixes gh-4386
Closes gh-4387

9 files changed, 41 insertions, 144 deletions

diff --git a/src/ajax.js b/src/ajax.js
index 9db26f66c..31880032d 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -458,6 +458,12 @@ jQuery.extend( {
 						if ( !responseHeaders ) {
 							responseHeaders = {};
 							while ( ( match = rheaders.exec( responseHeadersString ) ) ) {
+
+								// Support: IE 11+
+								// `getResponseHeader( key )` in IE doesn't combine all header
+								// values for the provided key into a single result with values
+								// joined by commas as other browsers do. Instead, it returns
+								// them on separate lines.
 								responseHeaders[ match[ 1 ].toLowerCase() + " " ] =
 									( responseHeaders[ match[ 1 ].toLowerCase() + " " ] || [] )
 										.concat( match[ 2 ] );
diff --git a/src/attributes/attr.js b/src/attributes/attr.js
index 6b5cbd2c4..cd2b3128b 100644
--- a/src/attributes/attr.js
+++ b/src/attributes/attr.js
@@ -2,10 +2,10 @@ define( [
 	"../core",
 	"../core/access",
 	"../core/nodeName",
-	"./support",
 	"../var/rnothtmlwhite",
+	"../var/isIE",
 	"../selector"
-], function( jQuery, access, nodeName, support, rnothtmlwhite ) {
+], function( jQuery, access, nodeName, rnothtmlwhite, isIE ) {
 
 "use strict";
 
@@ -74,8 +74,10 @@ jQuery.extend( {
 	attrHooks: {
 		type: {
 			set: function( elem, value ) {
-				if ( !support.radioValue && value === "radio" &&
-					nodeName( elem, "input" ) ) {
+
+				// Support: IE <=11+
+				// An input loses its value after becoming a radio
+				if ( isIE && value === "radio" && nodeName( elem, "input" ) ) {
 					var val = elem.value;
 					elem.setAttribute( "type", value );
 					if ( val ) {
diff --git a/src/attributes/prop.js b/src/attributes/prop.js
index 8ada707f4..71358aa92 100644
--- a/src/attributes/prop.js
+++ b/src/attributes/prop.js
@@ -1,9 +1,9 @@
 define( [
 	"../core",
 	"../core/access",
-	"./support",
+	"../var/isIE",
 	"../selector"
-], function( jQuery, access, support ) {
+], function( jQuery, access, isIE ) {
 
 "use strict";
 
@@ -90,14 +90,11 @@ jQuery.extend( {
 } );
 
 // Support: IE <=11+
-// Accessing the selectedIndex property
-// forces the browser to respect setting selected
-// on the option
-// The getter ensures a default option is selected
-// when in an optgroup
-// eslint rule "no-unused-expressions" is disabled for this code
-// since it considers such accessions noop
-if ( !support.optSelected ) {
+// Accessing the selectedIndex property forces the browser to respect
+// setting selected on the option. The getter ensures a default option
+// is selected when in an optgroup. ESLint rule "no-unused-expressions"
+// is disabled for this code since it considers such accessions noop.
+if ( isIE ) {
 	jQuery.propHooks.selected = {
 		get: function( elem ) {
 
diff --git a/src/attributes/support.js b/src/attributes/support.js
deleted file mode 100644
index 78d0040a9..000000000
--- a/src/attributes/support.js
+++ /dev/null
@@ -1,29 +0,0 @@
-define( [
-	"../var/document",
-	"../var/support"
-], function( document, support ) {
-
-"use strict";
-
-( function() {
-	var input = document.createElement( "input" ),
-		select = document.createElement( "select" ),
-		opt = select.appendChild( document.createElement( "option" ) );
-
-	input.type = "checkbox";
-
-	// Support: IE <=11+
-	// Must access selectedIndex to make default options select
-	support.optSelected = opt.selected;
-
-	// Support: IE <=11+
-	// An input loses its value after becoming a radio
-	input = document.createElement( "input" );
-	input.value = "t";
-	input.type = "radio";
-	support.radioValue = input.value === "t";
-} )();
-
-return support;
-
-} );
diff --git a/src/css.js b/src/css.js
index 91c42624e..2ae0c0c2c 100644
--- a/src/css.js
+++ b/src/css.js
@@ -2,6 +2,7 @@ define( [
 	"./core",
 	"./core/access",
 	"./var/rcssNum",
+	"./var/isIE",
 	"./css/var/rnumnonpx",
 	"./css/var/cssExpand",
 	"./css/isAutoPx",
@@ -10,14 +11,13 @@ define( [
 	"./css/var/swap",
 	"./css/curCSS",
 	"./css/adjustCSS",
-	"./css/support",
 	"./css/finalPropName",
 
 	"./core/init",
 	"./core/ready",
 	"./selector" // contains
-], function( jQuery, access, rcssNum, rnumnonpx, cssExpand, isAutoPx, cssCamelCase,
-	getStyles, swap, curCSS, adjustCSS, support, finalPropName ) {
+], function( jQuery, access, rcssNum, isIE, rnumnonpx, cssExpand, isAutoPx,
+	cssCamelCase, getStyles, swap, curCSS, adjustCSS, finalPropName ) {
 
 "use strict";
 
@@ -121,7 +121,7 @@ function getWidthOrHeight( elem, dimension, extra ) {
 
 		// To avoid forcing a reflow, only fetch boxSizing if we need it (gh-4322).
 		// Fake content-box until we know it's needed to know the true value.
-		boxSizingNeeded = !support.boxSizingReliable() || extra,
+		boxSizingNeeded = isIE || extra,
 		isBorderBox = boxSizingNeeded &&
 			jQuery.css( elem, "boxSizing", false, styles ) === "border-box",
 		valueIsBorderBox = isBorderBox,
@@ -140,11 +140,12 @@ function getWidthOrHeight( elem, dimension, extra ) {
 
 	// Fall back to offsetWidth/offsetHeight when value is "auto"
 	// This happens for inline elements with no explicit setting (gh-3571)
+	//
 	// Support: IE 9 - 11+
 	// Also use offsetWidth/offsetHeight for when box sizing is unreliable
 	// We use getClientRects() to check for hidden/disconnected.
 	// In those cases, the computed value can be trusted to be border-box
-	if ( ( !support.boxSizingReliable() && isBorderBox || val === "auto" ) &&
+	if ( ( isIE && isBorderBox || val === "auto" ) &&
 		elem.getClientRects().length ) {
 
 		isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box";
@@ -239,8 +240,9 @@ jQuery.extend( {
 				value += ret && ret[ 3 ] || ( isAutoPx( origName ) ? "px" : "" );
 			}
 
-			// background-* props affect original clone's values
-			if ( !support.clearCloneStyle && value === "" && name.indexOf( "background" ) === 0 ) {
+			// Support: IE <=9 - 11+
+			// background-* props of a cloned element affect the source element (#8908)
+			if ( isIE && value === "" && name.indexOf( "background" ) === 0 ) {
 				style[ name ] = "inherit";
 			}
 
diff --git a/src/css/support.js b/src/css/support.js
deleted file mode 100644
index 65763baec..000000000
--- a/src/css/support.js
+++ /dev/null
@@ -1,60 +0,0 @@
-define( [
-	"../core",
-	"../var/document",
-	"../var/documentElement",
-	"../var/support"
-], function( jQuery, document, documentElement, support ) {
-
-"use strict";
-
-( function() {
-
-	var boxSizingReliableVal,
-		container = document.createElement( "div" ),
-		div = document.createElement( "div" );
-
-	// Finish early in limited (non-browser) environments
-	if ( !div.style ) {
-		return;
-	}
-
-	// Support: IE <=9 - 11+
-	// Style of cloned element affects source element cloned (#8908)
-	div.style.backgroundClip = "content-box";
-	div.cloneNode( true ).style.backgroundClip = "";
-	support.clearCloneStyle = div.style.backgroundClip === "content-box";
-
-	jQuery.extend( support, {
-		boxSizingReliable: function() {
-
-			// This is a singleton, we need to execute it only once
-			if ( div ) {
-				container.style.cssText = "position:absolute;left:-11111px;width:60px;" +
-					"margin-top:1px;padding:0;border:0";
-				div.style.cssText =
-					"position:relative;display:block;box-sizing:border-box;overflow:scroll;" +
-					"margin:auto;border:1px;padding:1px;" +
-					"width:60%;top:1%";
-				documentElement.appendChild( container ).appendChild( div );
-
-				var divStyle = window.getComputedStyle( div );
-
-				// Support: IE 9 - 11+
-				// Detect misreporting of content dimensions for box-sizing:border-box elements
-				boxSizingReliableVal = Math.round( parseFloat( divStyle.width ) ) === 36;
-
-				documentElement.removeChild( container );
-
-				// Nullify the div so it wouldn't be stored in the memory and
-				// it will also be a sign that checks already performed
-				div = null;
-			}
-
-			return boxSizingReliableVal;
-		}
-	} );
-} )();
-
-return support;
-
-} );
diff --git a/src/manipulation.js b/src/manipulation.js
index fb10ef5c2..cca3947ce 100644
--- a/src/manipulation.js
+++ b/src/manipulation.js
@@ -2,6 +2,7 @@ define( [
 	"./core",
 	"./core/isAttached",
 	"./var/concat",
+	"./var/isIE",
 	"./var/push",
 	"./var/rcheckableType",
 	"./core/access",
@@ -11,7 +12,6 @@ define( [
 	"./manipulation/getAll",
 	"./manipulation/setGlobalEval",
 	"./manipulation/buildFragment",
-	"./manipulation/support",
 
 	"./data/var/dataPriv",
 	"./data/var/dataUser",
@@ -23,9 +23,9 @@ define( [
 	"./traversing",
 	"./selector",
 	"./event"
-], function( jQuery, isAttached, concat, push, rcheckableType,
-	access, rtagName, rscriptType,
-	wrapMap, getAll, setGlobalEval, buildFragment, support,
+], function( jQuery, isAttached, concat, isIE, push,
+	rcheckableType, access, rtagName, rscriptType,
+	wrapMap, getAll, setGlobalEval, buildFragment,
 	dataPriv, dataUser, acceptData, DOMEval, nodeName ) {
 
 "use strict";
@@ -222,7 +222,7 @@ jQuery.extend( {
 			inPage = isAttached( elem );
 
 		// Fix IE cloning issues
-		if ( !support.noCloneChecked && ( elem.nodeType === 1 || elem.nodeType === 11 ) &&
+		if ( isIE && ( elem.nodeType === 1 || elem.nodeType === 11 ) &&
 				!jQuery.isXMLDoc( elem ) ) {
 
 			// We eschew Sizzle here for performance reasons: https://jsperf.com/getall-vs-sizzle/2
@@ -233,7 +233,7 @@ jQuery.extend( {
 
 				// Support: IE <=11+
 				// IE fails to set the defaultValue to the correct value when
-				// cloning other types of input fields
+				// cloning textareas.
 				if ( destElements[ i ].nodeName.toLowerCase() === "textarea" ) {
 					destElements[ i ].defaultValue = srcElements[ i ].defaultValue;
 				}
diff --git a/src/manipulation/support.js b/src/manipulation/support.js
deleted file mode 100644
index f2ff88e17..000000000
--- a/src/manipulation/support.js
+++ /dev/null
@@ -1,28 +0,0 @@
-define( [
-	"../var/document",
-	"../var/support"
-], function( document, support ) {
-
-"use strict";
-
-( function() {
-	var fragment = document.createDocumentFragment(),
-		div = fragment.appendChild( document.createElement( "div" ) ),
-		input = document.createElement( "input" );
-
-	// Support: Windows Web Apps (WWA)
-	// `name` and `type` must use .setAttribute for WWA (#14901)
-	input.setAttribute( "type", "radio" );
-	input.setAttribute( "checked", "checked" );
-
-	div.appendChild( input );
-
-	// Support: IE <=11+
-	// Make sure textarea (and checkbox) defaultValue is properly cloned
-	div.innerHTML = "<textarea>x</textarea>";
-	support.noCloneChecked = !!div.cloneNode( true ).lastChild.defaultValue;
-} )();
-
-return support;
-
-} );
diff --git a/src/var/isIE.js b/src/var/isIE.js
new file mode 100644
index 000000000..e6a37cb5a
--- /dev/null
+++ b/src/var/isIE.js
@@ -0,0 +1,7 @@
+define( [
+	"./document"
+], function( document ) {
+	"use strict";
+
+	return document.documentMode;
+} );