Create a Lite Page bit for previews and fallback to Lo-Fi

chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc

Index: chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
diff --git a/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc b/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
index 154f28f0fc415a463a836944ad95249484fa5bc8..d29edfedb72b17b013d97591b35c9fe9fa95b8c5 100644
--- a/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
+++ b/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
@@ -863,12 +863,21 @@ content::PreviewsState ChromeResourceDispatcherHostDelegate::GetPreviewsState(
   data_reduction_proxy::DataReductionProxyIOData* data_reduction_proxy_io_data =
       io_data->data_reduction_proxy_io_data();
 
-  if (data_reduction_proxy_io_data) {
-    return data_reduction_proxy_io_data->ShouldEnableLoFiMode(url_request)
-               ? content::SERVER_LOFI_ON
-               : content::PREVIEWS_OFF;
+  content::PreviewsState previews_state = content::PREVIEWS_UNSPECIFIED;

[bengr, 2017/02/15 00:03:47]

Why do you need separate values for UNSPECIFIED and OFF?

[megjablon, 2017/02/16 04:29:09]

For requesting the original page with previews off. When we do that set
PREVIEWS_OFF on the navigation request so that we don't call the code to get the
preview state here.

https://cs.chromium.org/chromium/src/content/browser/loader/resource_dispatch...

+
+  if (data_reduction_proxy_io_data &&

[bengr, 2017/02/15 00:03:47]

Style nit:

if (drp_io_data) {
  if (drp_io_data->ShouldEnableFoo(request)
    previews_state |= LOFI_ON;
  if (drp_io_data->ShouldEnableBar(request)
    previews_state |= LITE_PAGE_ON;

[megjablon, 2017/02/16 04:29:09]

Done.

+      data_reduction_proxy_io_data->ShouldEnableLoFi(url_request)) {
+    previews_state |= content::SERVER_LOFI_ON;
+  }
+
+  if (data_reduction_proxy_io_data &&
+      data_reduction_proxy_io_data->ShouldEnableLitePages(url_request)) {
+    previews_state |= content::SERVER_LITE_PAGE_ON;
   }
-  return content::PREVIEWS_OFF;
+
+  if (previews_state == content::PREVIEWS_UNSPECIFIED)
+    return content::PREVIEWS_OFF;
+  return previews_state;
 }
 
 // static