Move MimeTypeResourceHandler before ThrottlingResourceHandler

content/browser/loader/replacing_resource_handler.h

Index: content/browser/loader/replacing_resource_handler.h
diff --git a/content/browser/loader/replacing_resource_handler.h b/content/browser/loader/replacing_resource_handler.h
new file mode 100644
index 0000000000000000000000000000000000000000..aa15c18774f9dbb9a91636e117479c2e13a3a924
--- /dev/null
+++ b/content/browser/loader/replacing_resource_handler.h
@@ -0,0 +1,97 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_LOADER_REPLACING_RESOURCE_HANDLER_H_
+#define CONTENT_BROWSER_LOADER_REPLACING_RESOURCE_HANDLER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "content/browser/loader/layered_resource_handler.h"
+#include "content/common/content_export.h"
+
+namespace net {
+class URLRequest;
+}
+
+namespace content {
+class PluginService;
+class ResourceDispatcherHostImpl;
+struct WebPluginInfo;
+
+// ResourceHandler that initiates special handling of the response if needed,
+// based on the response's MIME type (starts downloads, sends data to some
+// plugin types via a special channel).
+class CONTENT_EXPORT ReplacingResourceHandler : public LayeredResourceHandler {

[mmenke, 2016/06/09 18:09:29]

I'm not a big fan of this name.  ResourceHandlerReplacing[Resource]Handler seems
unwieldy.  RedirectingResourceHandler seems potentially confusing, given that
"redirect" could mean redirect in an HTTP-sense.  Maybe
InterceptingResourceHandler?  Open to other ideas.

[clamy, 2016/06/21 16:14:15]

Done.

+ public:
+  // If ENABLE_PLUGINS is defined, |plugin_service| must not be NULL.
+  ReplacingResourceHandler(std::unique_ptr<ResourceHandler> next_handler,
+                           ResourceDispatcherHostImpl* host,
+                           PluginService* plugin_service,
+                           net::URLRequest* request);
+  ~ReplacingResourceHandler() override;
+
+ private:
+  enum class State {

[mmenke, 2016/06/09 18:09:29]

I think these states need some documentation.

[clamy, 2016/06/21 16:14:15]

Done.

+    STARTING,
+    WAITING_FOR_NEW_HANDLER,

[mmenke, 2016/06/09 18:09:29]

We only keep this state when we're waiting to get a copy of the plugin list,
right?  So maybe name this to WAITING_FOR_PLUGINS, and only set the state to
this when the information returned by plugin_service_->GetPluginInfo is stale?

[clamy, 2016/06/21 16:14:15]

Done.

+    WAITING_FOR_BUFFER_COPY,

[mmenke, 2016/06/09 18:09:29]

This state is only needed because the MimeTypeResourceHandler calls
OnWillRequest before it calls OnResponseStarted, think that warrants a mention.

[clamy, 2016/06/21 16:14:15]

Done.

+    CHOICE_MADE,

[mmenke, 2016/06/09 18:09:29]

We've also made the choice in WAITING_FOR_BUFFER_COPY.  Maybe just call it
PASS_THROUGH or something?  Though that may imply we're passing through to the
original handler....

[clamy, 2016/06/21 16:14:15]

I've called it DONE, since the InterceptingResourceHandler is no longer doing
anything. I can change it to PASS_THROUGH if you prefer.

+  };

[mmenke, 2016/06/09 18:09:29]

nit:  Suggest a blank line here.

[clamy, 2016/06/21 16:14:15]

Done.

+  // ResourceHandler implementation:
+  bool OnResponseStarted(ResourceResponse* response, bool* defer) override;
+  bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
+                  int* buf_size,
+                  int min_size) override;
+  bool OnReadCompleted(int bytes_read, bool* defer) override;
+
+  bool MakeHandlerChoice(bool* defer);
+
+  // Determines whether a plugin will handle the current request, and if so,
+  // sets up the handler to direct the response to that plugin. Returns false
+  // if there is an error and the request should be cancelled and true
+  // otherwise. |defer| is set to true if plugin data is stale and needs to be
+  // refreshed before the request can be handled (in this case the function
+  // still returns true). If the request is directed to a plugin,
+  // |handled_by_plugin| is set to true.
+  bool SelectPluginHandler(bool* defer, bool* handled_by_plugin);
+  // Returns false if the request should be cancelled.
+  bool SelectNextHandler(bool* defer);
+  bool UseAlternateNextHandler(std::unique_ptr<ResourceHandler> handler,
+                               const std::string& payload_for_old_handler);
+
+  bool MustDownload();
+
+  // Called on the IO thread once the list of plugins has been loaded.
+  void OnPluginsLoaded(const std::vector<WebPluginInfo>& plugins);
+
+  bool CopyReadBufferToNextHandler();
+
+  State state_;
+
+  ResourceDispatcherHostImpl* host_;
+#if defined(ENABLE_PLUGINS)
+  PluginService* plugin_service_;
+#endif
+
+  bool switched_handler_;
+
+  bool must_download_;
+  bool must_download_is_set_;
+
+  // Used to copy data to the new next ResourceHandler.
+  scoped_refptr<ResourceResponse> response_;
+  scoped_refptr<net::IOBuffer> read_buffer_;
+  int bytes_read_;
+
+  base::WeakPtrFactory<ReplacingResourceHandler> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReplacingResourceHandler);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_REPLACING_RESOURCE_HANDLER_H_