Prevent mixed content iframes on back/forward.

third_party/WebKit/Source/platform/exported/WebMixedContent.cpp

Index: third_party/WebKit/Source/platform/exported/WebMixedContent.cpp
diff --git a/third_party/WebKit/Source/platform/exported/WebMixedContent.cpp b/third_party/WebKit/Source/platform/exported/WebMixedContent.cpp
index 1aac75dd75dadeccf7bad218f692e148d9cef61b..cd11497a3f4ab4acdde1a7822b2ed36800f0afa4 100644
--- a/third_party/WebKit/Source/platform/exported/WebMixedContent.cpp
+++ b/third_party/WebKit/Source/platform/exported/WebMixedContent.cpp
@@ -61,6 +61,7 @@ WebMixedContent::ContextType WebMixedContent::contextTypeFromRequestContext(WebU
     case WebURLRequest::RequestContextIframe:
     case WebURLRequest::RequestContextImageSet:
     case WebURLRequest::RequestContextImport:
+    case WebURLRequest::RequestContextInternal:

[Charlie Reis, 2016/08/01 23:39:16]

Is this safe?

[Mike West, 2016/08/02 07:41:51]

I wouldn't have thought so, though it surprises me that all the tests pass.
"Internal" was more or less a dumping ground for all the kinds of requests that
got missed when we made an initial pass through the codebase to tag requests
with contextual information. If we _can_ make this change, we should, as it's a
safer default. Jochen likes to say "No test, no feature." I'm inclined to agree.
:) 

I agree with your assessment of the rest. LGTM % logging cruft. :)

     case WebURLRequest::RequestContextLocation:
     case WebURLRequest::RequestContextManifest:
     case WebURLRequest::RequestContextObject:
@@ -78,7 +79,6 @@ WebMixedContent::ContextType WebMixedContent::contextTypeFromRequestContext(WebU
 
     // FIXME: Contexts that we should block, but don't currently. https://crbug.com/388650
     case WebURLRequest::RequestContextDownload:
-    case WebURLRequest::RequestContextInternal:
     case WebURLRequest::RequestContextPrefetch:
         return ContextType::ShouldBeBlockable;