Change Lo-Fi bool to bitmask to support multiple Previews types

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 a2f943e4c801cb410424d447e87c0e70912f6476..6a0a0ac5665c5c799f43446ed0c2d1fb7073d504 100644
--- a/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
+++ b/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
@@ -65,6 +65,7 @@
 #include "content/public/browser/service_worker_context.h"
 #include "content/public/browser/stream_info.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/common/previews_state.h"
 #include "content/public/common/resource_response.h"
 #include "extensions/features/features.h"
 #include "net/base/load_flags.h"
@@ -827,16 +828,23 @@ void ChromeResourceDispatcherHostDelegate::RequestComplete(
                  base::TimeTicks::Now() - url_request->creation_time()));
 }
 
-bool ChromeResourceDispatcherHostDelegate::ShouldEnableLoFiMode(
+int ChromeResourceDispatcherHostDelegate::GetPreviewsState(
+    int previews_state,
     const net::URLRequest& url_request,
     content::ResourceContext* resource_context) {
-  ProfileIOData* io_data = ProfileIOData::FromResourceContext(resource_context);
-  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);
-  return false;
+  if (previews_state & content::PREVIEWS_UNSPECIFIED) {

[RyanSturm, 2016/12/03 00:28:11]

Can you add a comment that previews_state is content::PREVIEWS_OFF when
reloading with LoFi disabled? When a new preview is added, I want it clear that
either they have to follow the reload with lofi off pattern for the preview, or
they should be aware that they might have define a preview state for LOFI_OFF
that their preview type could ignore here.

[megjablon, 2016/12/06 00:59:18]

Added the comment to resource_dispatcher_host_impl.cc since removing
PREVIEWS_UNSPECIFIED allowed me to go back to the original logic where
ChromeResourceDispatcherHostDelegate::GetPreviewsState isn't called unless the
state is "unspecified" (now 0).

+    ProfileIOData* io_data =
+        ProfileIOData::FromResourceContext(resource_context);
+    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;
+    return content::PREVIEWS_OFF;
+  }
+  return previews_state;
 }
 
 // static