Drop GetFrame()->GetDocument() usage in FrameFetchContext

third_party/WebKit/Source/core/loader/BaseFetchContext.cpp

Index: third_party/WebKit/Source/core/loader/BaseFetchContext.cpp
diff --git a/third_party/WebKit/Source/core/loader/BaseFetchContext.cpp b/third_party/WebKit/Source/core/loader/BaseFetchContext.cpp
index ae92738c45035ba21a2f10cfb4fb665d77eb75c2..7134f9cfb4d51349a7bc472347142dbb5a177979 100644
--- a/third_party/WebKit/Source/core/loader/BaseFetchContext.cpp
+++ b/third_party/WebKit/Source/core/loader/BaseFetchContext.cpp
@@ -257,13 +257,16 @@ ResourceRequestBlockedReason BaseFetchContext::CanRequestInternal(
   // Measure the number of legacy URL schemes ('ftp://') and the number of
   // embedded-credential ('http://user:password@...') resources embedded as
   // subresources.
-  if (resource_request.GetFrameType() != WebURLRequest::kFrameTypeTopLevel) {
-    if (GetMainResourceSecurityContext() &&
-        SchemeRegistry::ShouldTreatURLSchemeAsLegacy(url.Protocol()) &&
+  WebURLRequest::FrameType frame_type = resource_request.GetFrameType();
+  if (frame_type != WebURLRequest::kFrameTypeTopLevel) {
+    bool is_subresource = frame_type == WebURLRequest::kFrameTypeNone;
+    SecurityContext* embedding_context =
+        is_subresource ? &execution_context_->GetSecurityContext()
+                       : GetParentSecurityContext();

[Nate Chapin, 2017/04/28 21:33:31]

The only reason GetMainResourceSecurityContext() needed to reference
GetFrame()->GetDocument() was to handle the iframe load case. In that case,
there must be a parent with a valid SecurityContext (whether local or remote),
and technically the parent is what's embedding things we want to deprecate
anyway. Reference this frame's for subresources, and the parent's for iframe
main resources.

[kinuko, 2017/04/29 14:10:20]

This is much clearer now, thanks!

+    DCHECK(embedding_context);
+    if (SchemeRegistry::ShouldTreatURLSchemeAsLegacy(url.Protocol()) &&
         !SchemeRegistry::ShouldTreatURLSchemeAsLegacy(
-            GetMainResourceSecurityContext()
-                ->GetSecurityOrigin()
-                ->Protocol())) {
+            embedding_context->GetSecurityOrigin()->Protocol())) {
       CountDeprecation(UseCounter::kLegacyProtocolEmbeddedAsSubresource);
 
       // TODO(mkwst): Enabled by default in M59. Drop the runtime-enabled check