Move UKM PageLoad SourceId generation to PageLoadTracker.

chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc

Index: chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc
diff --git a/chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc b/chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc
index dd8592193b71f0dbc49d9029d338c3dc7a7070b0..3a1b844d8a4b1e78573a3c6b3d96e38aaf91bca4 100644
--- a/chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc
+++ b/chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc
@@ -100,7 +100,8 @@ class FilteringPageLoadMetricsObserver : public PageLoadMetricsObserver {
     return should_ignore ? STOP_OBSERVING : CONTINUE_OBSERVING;
   }
 
-  ObservePolicy OnCommit(content::NavigationHandle* handle) override {
+  ObservePolicy OnCommit(content::NavigationHandle* handle,
+                         ukm::SourceId source_id) override {
     const bool should_ignore =
         handle->GetURL().spec().find("ignore-on-commit") != std::string::npos;
     return should_ignore ? STOP_OBSERVING : CONTINUE_OBSERVING;