Breakout perspective for better IE11 support. (#594)

test/core_tests.js

@@ -37,9 +37,10 @@
     });
 
     QUnit.test( "Attributes", function( assert ) {
-      assert.expect( 9 );
+      assert.expect( 10 );
 
       var actual, expected;
+      var root = document.querySelector( "#impress" );
       var canvas = document.querySelector( "div#impress > div" );
 
       var canvasIsNotAStep = !canvas.classList.contains("step") && canvas.id === "";
@@ -78,6 +79,10 @@
       expected = "ease-in-out";
       assert.strictEqual( actual, expected, "canvas.style.transitionTimingFunction initialized correctly" );
 
+      actual = root.style.perspective;
+      expected = "";
+      assert.notStrictEqual( actual, expected, "root.style.perspective should be set explicitly for IE 11" );
+
       actual = document.documentElement.style.height;
       expected = "100%";
       assert.strictEqual( actual, expected, "documentElement.style.height is 100%" );