Report frequency of single page app navigations to UMA

third_party/WebKit/Source/core/loader/FrameLoader.cpp

Index: third_party/WebKit/Source/core/loader/FrameLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/FrameLoader.cpp b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
index 23b058dc70155aed38401d5d15f0860ebd8d6adb..0b4a7d5f802e705c67221735984e7c20c11aee69 100644
--- a/third_party/WebKit/Source/core/loader/FrameLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
@@ -79,6 +79,7 @@
 #include "core/probe/CoreProbes.h"
 #include "core/svg/graphics/SVGImage.h"
 #include "core/xml/parser/XMLDocumentParser.h"
+#include "platform/Histogram.h"
 #include "platform/InstanceCounters.h"
 #include "platform/PluginScriptForbiddenScope.h"
 #include "platform/ScriptForbiddenScope.h"
@@ -484,6 +485,33 @@ void FrameLoader::UpdateForSameDocumentNavigation(
     HistoryScrollRestorationType scroll_restoration_type,
     FrameLoadType type,
     Document* initiating_document) {
+  // |SinglePageAppNavigationType| falls into this grid according to different
+  // combinations of |FrameLoadType| and |SameDocumentNavigationSource|:
+  //
+  //                              HistoryApi           Default
+  //  kFrameLoadTypeBackForward   illegal              otherFragmentNav
+  // !kFrameLoadTypeBackForward   sameDocBack/Forward  historyPushOrReplace
+  SinglePageAppNavigationType single_page_app_navigation_type;
+  switch (same_document_navigation_source) {
+    case kSameDocumentNavigationDefault:
+      if (type == kFrameLoadTypeBackForward) {
+        single_page_app_navigation_type =
+            kSPANavTypeSameDocumentBackwardOrForward;
+      } else {
+        single_page_app_navigation_type = kSPANavTypeOtherFragmentNavigation;
+      }
+      break;
+    case kSameDocumentNavigationHistoryApi:
+      // It's illegal to have both kSameDocumentNavigationHistoryApi and
+      // kFrameLoadTypeBackForward.
+      DCHECK(type != kFrameLoadTypeBackForward);
+      single_page_app_navigation_type =
+          kSPANavTypeHistoryPushStateOrReplaceState;
+  }
+  UMA_HISTOGRAM_ENUMERATION(
+      "RendererScheduler.UpdateForSameDocumentNavigationCount",
+      single_page_app_navigation_type, kSPANavTypeCount);
+
   TRACE_EVENT1("blink", "FrameLoader::updateForSameDocumentNavigation", "url",
                new_url.GetString().Ascii().data());