Ensure we never remove the style attribute when syncing it from CSSOM.

third_party/WebKit/LayoutTests/editing/execCommand/script-tests/empty-span-removal.js

 description("Test to make sure we remove span tags with no attributes if we removed the last attribute.")
 
 var testContainer = document.createElement("div");
 testContainer.contentEditable = true;
 document.body.appendChild(testContainer);
 
 function testSingleToggle(toggleCommand, initialContents, expectedContents)
 {
     testContainer.innerHTML = initialContents;
     window.getSelection().selectAllChildren(testContainer);
@@ skipping 14 matching lines @@
     if (testContainer.innerHTML === expectedContents) {
         testPassed("two " + toggleCommand + " commands converted " + initialContents + " to " + expectedContents);
     } else {
         testFailed("two " + toggleCommand + " commands converted " + initialContents + " to " + testContainer.innerHTML + ", expected " + expectedContents);
     }
 }
 
 testSingleToggle("bold", "<span><span style='font-weight: bold'>test</span></span>", "<span>test</span>");
 testSingleToggle("bold", "<span style='font-weight: bold'><span>test</span></span>", "test");
 testSingleToggle("bold", "<span style='font-weight: bold'><span style='font-weight: bold'>test</span></span>", "test");
-testSingleToggle("bold", "<span foo=\"bar\" style='font-weight: bold'>test</span>", "<span foo=\"bar\">test</span>");
+testSingleToggle("bold", "<span foo=\"bar\" style='font-weight: bold'>test</span>", "<span foo=\"bar\" style=\"\">test</span>");
 testDoubleToggle("bold", "<span>test</span>", "<span>test</span>");
 
 document.body.removeChild(testContainer);
 
 var successfullyParsed = true;