Use the correct node when hit testing on an image map

LayoutTests/fast/replaced/image-map-alt-content-crash.html

Index: LayoutTests/fast/replaced/image-map-alt-content-crash.html
diff --git a/LayoutTests/fast/replaced/image-map-alt-content-crash.html b/LayoutTests/fast/replaced/image-map-alt-content-crash.html
new file mode 100644
index 0000000000000000000000000000000000000000..eb19061dfb6bbbf9025f5c757e93754b4ce48407
--- /dev/null
+++ b/LayoutTests/fast/replaced/image-map-alt-content-crash.html
@@ -0,0 +1,10 @@
+<a onmouseover="var img=document['mapimage'];img.src=img.lowsrc?img.lowsrc:img.getAttribute?img.getAttribute('lowsrc'):img.src;">
+		<img alt="alt text" width="850" usemap="#map" name="mapimage">
+<map name="map"><area shape="rect" coords="60,60,100,100"></map>
+<p>crbug.com/482214: Don't crash when hit testing while moving across a broken image that contains an image map.</p>
+<script>
+if (window.testRunner) {
+    testRunner.dumpAsText();
+    eventSender.mouseMoveTo(50, 50);
+}
+</script>