Re-instantiate the mixed iframe block for M30.

Source/core/loader/DocumentLoader.cpp

Index: Source/core/loader/DocumentLoader.cpp
diff --git a/Source/core/loader/DocumentLoader.cpp b/Source/core/loader/DocumentLoader.cpp
index ec95a4b90631bb53591a937a568e9a43d5b7c555..f16780473ae55be643fd1f1fe75ffb460fd48e4c 100644
--- a/Source/core/loader/DocumentLoader.cpp
+++ b/Source/core/loader/DocumentLoader.cpp
@@ -479,9 +479,9 @@ void DocumentLoader::willSendRequest(ResourceRequest& newRequest, const Resource
     if (newRequest.cachePolicy() == UseProtocolCachePolicy && isPostOrRedirectAfterPost(newRequest, redirectResponse))
         newRequest.setCachePolicy(ReloadIgnoringCacheData);
 
-    Frame* top = m_frame->tree()->top();
-    if (top) {
-        if (!top->loader()->mixedContentChecker()->canDisplayInsecureContent(top->document()->securityOrigin(), newRequest.url())) {
+    Frame* parent = m_frame->tree()->parent();
+    if (parent) {
+        if (!parent->loader()->mixedContentChecker()->canRunInsecureContent(parent->document()->securityOrigin(), newRequest.url())) {
             cancelMainResourceLoad(ResourceError::cancelledError(newRequest.url()));
             return;
         }