Consistently use LoFi for an entire page

net/url_request/url_request.h

Index: net/url_request/url_request.h
diff --git a/net/url_request/url_request.h b/net/url_request/url_request.h
index c6ef160e69c4fb2ace304bc27e9af0cbe6c972a9..bc6dcca14eb73c5e17215fe1554f77b5b20e84e8 100644
--- a/net/url_request/url_request.h
+++ b/net/url_request/url_request.h
@@ -60,6 +60,17 @@ class X509Certificate;
 // 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.
 //
@@ -298,6 +309,11 @@ class NET_EXPORT URLRequest : NON_EXPORTED_BASE(public base::NonThreadSafe),
   // 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();
@@ -829,6 +845,10 @@ class NET_EXPORT URLRequest : NON_EXPORTED_BASE(public base::NonThreadSafe),
 
   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);
 };