[import] support document.stylesheets in imported documents.

LayoutTests/fast/html/imports/import-style-basic.html

Index: LayoutTests/fast/html/imports/import-style-basic.html
diff --git a/LayoutTests/fast/html/imports/import-style-basic.html b/LayoutTests/fast/html/imports/import-style-basic.html
index f819122f7b37fdc40882607fa9d4fa2db1d3c373..65944d726204aee3b584eb8bcbd61ef34fd3e1cd 100644
--- a/LayoutTests/fast/html/imports/import-style-basic.html
+++ b/LayoutTests/fast/html/imports/import-style-basic.html
@@ -23,8 +23,11 @@
 <script>
 window.jsTestIsAsync = true;
 
-// CSSOM contains master's sheets only.
+// Master's CSSOM contains master's sheets only.
 shouldBe("document.styleSheets.length", "2"); // Extra one comes from js-test.js
+// Import's CSS should have its own
+shouldBe("importLink.import.styleSheets.length", "1");
+
 // a trivial case
 shouldBeEqualToString("window.getComputedStyle(shouldBeBlue).color", "rgb(0, 0, 255)");
 // Nested case
@@ -40,18 +43,22 @@ var styleWithGreen = importLink.import.createElement("style");
 styleWithGreen.innerHTML = ".green-from-import { color: green; }";
 importLink.import.head.appendChild(styleWithGreen);
 shouldBeEqualToString("window.getComputedStyle(shouldBeGreen).color", "rgb(0, 128, 0)");
+shouldBe("importLink.import.styleSheets.length", "2");
 
 // Dyanically removing
 Array.prototype.forEach.call(importLink.import.querySelectorAll("style"), function(e) { e.remove(); });
 shouldBeEqualToString("window.getComputedStyle(shouldBeBlue).color", "rgb(0, 0, 0)");
 shouldBeEqualToString("window.getComputedStyle(shouldBeGreen).color", "rgb(0, 0, 0)");
+shouldBe("importLink.import.styleSheets.length", "0");
 
 // Dymically adding an import
 var dynamicLink = document.createElement("link");
 dynamicLink.setAttribute("rel", "import");
+dynamicLink.id = "importLinkDynamic";
 dynamicLink.setAttribute("href", "resources/style-basic-child-dynamic.html");
 dynamicLink.onload = function() {
     shouldBeEqualToString("window.getComputedStyle(shouldBeAqua).color", "rgb(0, 255, 255)");
+    shouldBe("importLinkDynamic.import.styleSheets.length", "1");
     finishJSTest();
 };