Add a way to send the resource percentage signal to the RC.

chrome/browser/android/offline_pages/prerendering_loader.cc

Index: chrome/browser/android/offline_pages/prerendering_loader.cc
diff --git a/chrome/browser/android/offline_pages/prerendering_loader.cc b/chrome/browser/android/offline_pages/prerendering_loader.cc
index 5eccbf9f696600b8045c7cfbf5e1cf3c315d6fe7..fd31ed8a0f7d13cf69cda47b6b7cb570fcc4ea50 100644
--- a/chrome/browser/android/offline_pages/prerendering_loader.cc
+++ b/chrome/browser/android/offline_pages/prerendering_loader.cc
@@ -88,6 +88,17 @@ void PrerenderingLoader::AddLoadingSignal(const char* signal_name) {
   signal_data_.SetDouble(signal_name, delay);
 }
 
+void PrerenderingLoader::AddResourceSignal(const ResourceDataType type,

[Dmitry Titov, 2017/05/18 02:28:10]

It is not clear why these are called "Add*" when they constantly re-set the
values, since they are called up to 2 times per each loaded resource... Would it
be better to call them SetResourceSignal?

[Pete Williamson, 2017/05/24 01:01:50]

Moved the content into ObserverResourceTracking everywhere.

+                                           int64_t started_count,
+                                           int64_t completed_count) {
+  double percentage = 100 * static_cast<double>(completed_count) /
+                      static_cast<double>(started_count);
+  // TODO(petewil): Use actual signal type instead of hardcoding name to image.
+  signal_data_.SetDouble("ImagePercentage", percentage);
+  signal_data_.SetDouble("StartedImages", started_count);
+  signal_data_.SetDouble("CompletedImages", completed_count);
+}
+
 bool PrerenderingLoader::LoadPage(const GURL& url,
                                   const LoadPageCallback& load_done_callback,
                                   const ProgressCallback& progress_callback) {
@@ -199,6 +210,14 @@ bool PrerenderingLoader::IsLowbarMet() {
   return is_lowbar_met_;
 }
 
+void PrerenderingLoader::ObserveResourceTracking(const ResourceDataType type,
+                                                 int64_t started_count,
+                                                 int64_t completed_count) {
+  // Add the signal to extra data, and use for tracking.
+  if (type == ResourceDataType::IMAGE)

[Dmitry Titov, 2017/05/18 02:28:10]

This conditional can go to AddResourceSignal where the rest of the logic is,
then this method can be just removed.

[Pete Williamson, 2017/05/24 01:01:50]

Kept this method, since it is the exposed interface method, but moved
AddResourceSignal into here.

+    AddResourceSignal(type, started_count, completed_count);
+}
+
 void PrerenderingLoader::HandleLoadEvent() {
   // If still loading, check if the load succeeded or not, then update
   // the internal state (LOADED for success or IDLE for failure) and post