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

chrome/browser/page_load_metrics/page_load_metrics_initialize.cc

Index: chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc b/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
index 19e9a9f30ad8ff88ebe75e454f8aa84f98c9b11b..fa66f63f0dd2b44f35aef3e1db42c8db72c87b27 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
@@ -4,8 +4,12 @@
 
 #include "chrome/browser/page_load_metrics/page_load_metrics_initialize.h"
 
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#if defined(OS_ANDROID)
+#include "chrome/browser/android/offline_pages/request_coordinator_factory.h"
+#endif
 #include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 #if defined(OS_ANDROID)
 #include "chrome/browser/page_load_metrics/observers/android_page_load_metrics_observer.h"
@@ -28,6 +32,7 @@
 #include "chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/protocol_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/resource_prefetch_predictor_page_load_metrics_observer.h"
+#include "chrome/browser/page_load_metrics/observers/resource_tracking_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/tab_restore_page_load_metrics_observer.h"
@@ -37,6 +42,9 @@
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search/search.h"
+#if defined(OS_ANDROID)
+#include "components/offline_pages/core/background/request_coordinator.h"
+#endif
 #include "components/rappor/rappor_service_impl.h"
 #include "content/public/browser/web_contents.h"
 #include "url/gurl.h"
@@ -132,6 +140,19 @@ void PageLoadMetricsEmbedder::RegisterObservers(
       base::MakeUnique<OmniboxSuggestionUsedMetricsObserver>(IsPrerendering()));
   tracker->AddObserver(
       base::MakeUnique<DelayNavigationPageLoadMetricsObserver>());
+#if defined(OS_ANDROID)
+  // Whether we are using the pre-renderer or not, set up a
+  // ResourceTrackingPageLoadMetricsObserver.
+  offline_pages::RequestCoordinator* request_coordinator =

[RyanSturm, 2017/05/10 15:55:53]

Can you move the code to get the RequestCoordinator into OnStart of
ResourceTrackingPageLoadMetricsObserver (it's called on the same stack as the
constructor).

[Pete Williamson, 2017/05/10 18:14:53]

I originally did this for dependency injection to make the code more testable. 
I can change it as you suggest, but then I'm not sure how to unit test the
ResourceTrackingPageLoadMetricsObserver - do you know any techniques to mock out
getting a keyed service in a unit test?  I would think it required enough of
chrome to be a full browser test at that point.

[RyanSturm, 2017/05/10 18:30:13]

That's a valid point. I've done some other hacky approaches here using
virtualization:
https://cs.chromium.org/chromium/src/chrome/browser/page_load_metrics/observe...

If you are more comfortable with that approach, it keeps the boundaries a little
more clear. Generally, I agree dependency injection is better though, so I won't
push back.

+      offline_pages::RequestCoordinatorFactory::GetForBrowserContext(
+          web_contents_->GetBrowserContext());
+  if (request_coordinator) {
+    tracker->AddObserver(
+        base::MakeUnique<
+            page_load_metrics::ResourceTrackingPageLoadMetricsObserver>(
+            request_coordinator));
+  }
+#endif  // OS_ANDROID
 }
 
 bool PageLoadMetricsEmbedder::IsPrerendering() const {