Removing x-x509-user-cert mime handler.

content/browser/loader/mime_type_resource_handler.cc

Index: content/browser/loader/mime_type_resource_handler.cc
diff --git a/content/browser/loader/mime_type_resource_handler.cc b/content/browser/loader/mime_type_resource_handler.cc
index 59c2b5310660487b1a0ccdc7f9591da7ebcc14bc..674d6644f64f0bfe56a38c4df58117dae9091d66 100644
--- a/content/browser/loader/mime_type_resource_handler.cc
+++ b/content/browser/loader/mime_type_resource_handler.cc
@@ -16,7 +16,6 @@
 #include "components/mime_util/mime_util.h"
 #include "content/browser/download/download_resource_handler.h"
 #include "content/browser/download/download_stats.h"
-#include "content/browser/loader/certificate_resource_handler.h"
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 #include "content/browser/loader/resource_request_info_impl.h"
 #include "content/browser/loader/stream_resource_handler.h"
@@ -341,14 +340,6 @@ bool MimeTypeResourceHandler::SelectNextHandler(bool* defer) {
   ResourceRequestInfoImpl* info = GetRequestInfo();
   const std::string& mime_type = response_->head.mime_type;
 
-  if (mime_util::IsSupportedCertificateMimeType(mime_type)) {
-    // Install certificate file.
-    info->set_is_download(true);
-    scoped_ptr<ResourceHandler> handler(
-        new CertificateResourceHandler(request()));
-    return UseAlternateNextHandler(handler.Pass(), std::string());
-  }
-
   // Allow requests for object/embed tags to be intercepted as streams.
   if (info->GetResourceType() == content::RESOURCE_TYPE_OBJECT) {
     DCHECK(!info->allow_download());
@@ -371,8 +362,10 @@ bool MimeTypeResourceHandler::SelectNextHandler(bool* defer) {
 
   bool must_download = MustDownload();
   if (!must_download) {
-    if (mime_util::IsSupportedMimeType(mime_type))
+    if (mime_util::IsSupportedMimeType(mime_type) &&
+        !mime_util::IsSupportedCertificateMimeType(mime_type)) {

[Ryan Sleevi, 2015/12/01 22:45:47]

I'm not entirely clear why this is needed; shouldn't it be fine to force it as a
download?

[svaldez, 2015/12/01 22:53:36]

This is the escape hatch for files with MimeTypes we can handle separately.
Since we don't want to do that with Certificate files, we have to add the check
here.

[Ryan Sleevi, 2015/12/01 23:00:50]

I guess I'm still confused. Why don't we want to do that for Certificate files?

I guess put differently: Why wouldn't we simply remove certificates entirely
from IsSupportedMimeType?

[svaldez, 2015/12/01 23:05:22]

I believe that doesn't work since sites don't set Content-Disposition and the
browser ends up displaying the certificate instead of attempting to download it.

[Ryan Sleevi, 2015/12/01 23:15:56]

Well, not necessarily.

So, sorry, some hidden context here is the desire to get rid of the notion of
certificate mime types from being a special case, as much as possible. That's
the end goal, and any intermediate steps we can take to move towards that end
goal, rad.

I think it's not the end of the world if we have this check here, but the
alternative is that we remove it from IsSupportedMimeType(), and instead let it
be handled via the MustDownload (line 363). There, we let MustDownload() call to
the host (
https://code.google.com/p/chromium/codesearch#chromium/src/content/public/bro...
), which could then force it to be downloaded.

That said, I can see where embedders likely want to rely on the weird implicit
API contract we have now in //content (where they don't have to think about
certificates; which is a "bug" but *shrug*), so this is fine.

As an alternative way of thinking, would it make sense to mangle in a
Content-Disposition (and filename) if no C-D is present, at a lower layer in the
stack? I'm not sure if there's any clean opportunities to do that, but that'd be
another way of keeping some of that logic close.

All of this to say that, after the explanation and looking at the code more, I'm
able to live with the conditional as is and we can nuke it when we fully nuke
certificate support, but I'm also fond of removing as much as possible any
knowledge of certificates.

       return true;
+    }
 
     bool handled_by_plugin;
     if (!SelectPluginHandler(defer, &handled_by_plugin))