Add support for counting same-document AMP loads.

chrome/browser/page_load_metrics/page_load_tracker.cc

Index: chrome/browser/page_load_metrics/page_load_tracker.cc
diff --git a/chrome/browser/page_load_metrics/page_load_tracker.cc b/chrome/browser/page_load_metrics/page_load_tracker.cc
index 1b681d98303c90313c022b365ec7a555da4c94f9..dd67b60913c36f1b5cb3d1ba90ab09edd988ccce 100644
--- a/chrome/browser/page_load_metrics/page_load_tracker.cc
+++ b/chrome/browser/page_load_metrics/page_load_tracker.cc
@@ -544,10 +544,18 @@ void PageLoadTracker::Commit(content::NavigationHandle* navigation_handle) {
   LogAbortChainHistograms(navigation_handle);
 }
 
+void PageLoadTracker::DidCommitSameDocumentNavigation(
+    content::NavigationHandle* navigation_handle) {
+  for (const auto& observer : observers_) {
+    observer->OnCommitSameDocumentNavigation(navigation_handle);
+  }
+}
+
 void PageLoadTracker::DidFinishSubFrameNavigation(
     content::NavigationHandle* navigation_handle) {
-  INVOKE_AND_PRUNE_OBSERVERS(observers_, OnDidFinishSubFrameNavigation,
-                             navigation_handle);
+  for (const auto& observer : observers_) {
+    observer->OnDidFinishSubFrameNavigation(navigation_handle);
+  }
 
   if (!navigation_handle->HasCommitted())
     return;