Do not preload data URIs.

LayoutTests/http/tests/loading/preload-image-src.html

Index: LayoutTests/http/tests/loading/preload-image-src.html
diff --git a/LayoutTests/http/tests/loading/preload-image-src.html b/LayoutTests/http/tests/loading/preload-image-src.html
index aa54ca4b9d636e968e831f50f6bfb9867a3f83e7..ce28988234624e72c3bac4aa3df3d9bbd12c4371 100644
--- a/LayoutTests/http/tests/loading/preload-image-src.html
+++ b/LayoutTests/http/tests/loading/preload-image-src.html
@@ -8,10 +8,12 @@
     shouldBeTrue("internals.isPreloaded('resources/base-image1.png');");
     shouldBeTrue("internals.isPreloaded('resources/base-image2.png');");
     shouldBeFalse("internals.isPreloaded('resources/base-image3.png');");
+    shouldBeFalse("internals.isPreloaded('data:image/gif;base64,R0lGODlhAQABAIAAAP///////yH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==');");
 </script>
-<div>This test passes if the image (defined in the src attribute) is preloaded.</div>
+<div>This test passes if the image (defined in the src attribute) is preloaded, except for data URI.</div>
 <img src="resources/base-image1.png">
 <img src="resources/base-image2.png" src="resources/base-image3.png">
+<img src="data:image/gif;base64,R0lGODlhAQABAIAAAP///////yH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==">
 </body>
 </html>