Consistently use LoFi for an entire page

net/url_request/url_request.h

 // Copyright (c) 2012 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 NET_URL_REQUEST_URL_REQUEST_H_
 #define NET_URL_REQUEST_URL_REQUEST_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 42 matching lines @@
 class UploadDataStream;
 class URLRequestContext;
 class URLRequestJob;
 class X509Certificate;
 
 // This stores the values of the Set-Cookie headers received during the request.
 // Each item in the vector corresponds to a Set-Cookie: line received,
 // excluding the "Set-Cookie:" part.
 typedef std::vector<std::string> ResponseCookies;
 
+// The LoFi state which determines whether to add the LoFi header. Must stay
+// in sync with the enum in navigation_params.h.
+enum LoFiState {
+  // Request a LoFi version of the resource.
+  LOFI_ON = 0,
+  // Request a normal (non-LoFi) version of the resource.
+  LOFI_OFF,
+  // Let the browser process decide whether or not to request the LoFi version.
+  LOFI_DEFAULT,
+};
+
 //-----------------------------------------------------------------------------
 // A class  representing the asynchronous load of a data stream from an URL.
 //
 // The lifetime of an instance of this class is completely controlled by the
 // consumer, and the instance is not required to live on the heap or be
 // allocated in any special way.  It is also valid to delete an URLRequest
 // object during the handling of a callback to its delegate.  Of course, once
 // the URLRequest is deleted, no further callbacks to its delegate will occur.
 //
 // NOTE: All usage of all instances of this class should be on the same thread.
@@ skipping 218 matching lines @@
 
   // The referrer policy to apply when updating the referrer during redirects.
   // The referrer policy may only be changed before Start() is called.
   ReferrerPolicy referrer_policy() const { return referrer_policy_; }
   void set_referrer_policy(ReferrerPolicy referrer_policy);
 
   // Sets the delegate of the request.  This value may be changed at any time,
   // and it is permissible for it to be null.
   void set_delegate(Delegate* delegate);
 
+  // Whether or not to request a LoFi version of the resource or let the
+  // browser decide.
+  LoFiState lofi_state() const { return lofi_state_; }
+  void set_lofi_state(LoFiState lofi_state);
+
   // Indicates that the request body should be sent using chunked transfer
   // encoding. This method may only be called before Start() is called.
   void EnableChunkedUpload();
 
   // Appends the given bytes to the request's upload data to be sent
   // immediately via chunked transfer encoding. When all data has been added,
   // set |is_last_chunk| to true to indicate the end of upload data.  All chunks
   // but the last must have |bytes_len| > 0.
   //
   // This method may be called only after calling EnableChunkedUpload().
@@ skipping 511 matching lines @@
   LoadTimingInfo load_timing_info_;
 
   // Keeps track of whether or not OnBeforeNetworkStart has been called yet.
   bool notified_before_network_start_;
 
   // The proxy server used for this request, if any.
   HostPortPair proxy_server_;
 
   scoped_ptr<const base::debug::StackTrace> stack_trace_;
 
+  // Whether or not to request a LoFi version of the resource or let the
+  // browser decide.
+  LoFiState lofi_state_;

[davidben, 2015/08/27 18:53:50]

Why is this on the URLRequest? It's not used by //net at all. //net is not just
an HTTP stack for //content. Consumer-specific state needs to be in the
consumer. //net can't know about it while //content needs to, so this should be
in //content somewhere.

[megjablon, 2015/08/27 23:11:02]

We add q=low to the Chrome-Proxy header in
DataReductionProxyNetworkDelegate::OnBeforeSendProxyHeadersInternal which gets a
URLRequest. 

[davidben, 2015/08/31 23:43:24]

There's other ways to staple consumer-specific state, such as UserData. This CL
should not end up touching anything in //net.

[bengr, 2015/09/02 19:01:36]

I like this goal.

[megjablon, 2015/09/11 20:58:03]

Aren't there layering issues with creating and setting LoFi UserData in
//content and then getting it in //components? I don't know that this is
feasible.

[davidben, 2015/09/14 20:30:29]

Portions of //components can depend on //content, right? Just not the core
parts. So it should be possible to plumb that up.

Although, since //content has to track this bit and know about it, it seems
//content should have some interface out to its embedder for deciding when to
use lofi mode. Maybe a ShouldEnableLofiMode() hook on the
ResourceDispatcherHostDelegate or something which gets the ResourceContext or
similar.

Though that the interpretation of this bit is, to begin with, something that
//content can't do is also pretty wonky since you put it in the DRP's header. I
think the real problem is you're trying to coordinate too many related jobs
across too many layers, which is why the interfaces across layers get very
complex.

(This is why I'd been advocating having a separate header. Then //content can
know what that header means, insert it, and //chrome's and //components' role is
just in implementing the ShouldEnableLofiMode() hook.)

+
   DISALLOW_COPY_AND_ASSIGN(URLRequest);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_H_