preload: strip existing rel=preload hints

jeffkaufman · crowell · commit dbde98953a79 · 2016-07-13T16:25:53.000-04:00
Fixes #1327
diff --git a/net/instaweb/rewriter/strip_subresource_hints_filter.cc b/net/instaweb/rewriter/strip_subresource_hints_filter.cc
@@ -51,7 +51,9 @@ void StripSubresourceHintsFilter::StartElement(HtmlElement* element) {
 
   if (element->keyword() == HtmlName::kLink) {
     const char *value = element->AttributeValue(HtmlName::kRel);
-    if (value && StringCaseEqual(value, "subresource")) {
+    if (value && (
+            StringCaseEqual(value, "subresource") ||
+            StringCaseEqual(value, "preload"))) {
       const RewriteOptions *options = driver_->options();
       const char *resource_url = element->AttributeValue(HtmlName::kSrc);
       if (!resource_url) {
diff --git a/net/instaweb/rewriter/strip_subresource_hints_filter_test.cc b/net/instaweb/rewriter/strip_subresource_hints_filter_test.cc
@@ -156,6 +156,16 @@ TEST_F(StripSubresourceHintsFilterTest, SingleResourceValidLink) {
   ValidateStripSubresourceHint(source, rewritten);
 }
 
+TEST_F(StripSubresourceHintsFilterTest, SingleResourceValidPreloadLink) {
+  const char *source =
+    "<head><link rel=\"preload\" src=\"/test.gif\" as=\"image\"/></head>"
+    "<body><img src=\"1.jpg\"/></body>";
+  const char *rewritten =
+    "<head></head>"
+    "<body><img src=\"1.jpg\"/></body>";
+  ValidateStripSubresourceHint(source, rewritten);
+}
+
 TEST_F(StripSubresourceHintsFilterTest, SingleResourceExternalLink) {
   const char *source =
     "<head>"
