Report frequency of single page app navigations to UMA

third_party/WebKit/Source/core/loader/FrameLoaderTypes.h

Index: third_party/WebKit/Source/core/loader/FrameLoaderTypes.h
diff --git a/third_party/WebKit/Source/core/loader/FrameLoaderTypes.h b/third_party/WebKit/Source/core/loader/FrameLoaderTypes.h
index 97a514633ff62dd8ebcc23a2041c7031821d797b..2541108d1e78669dba6deb179762f04fb825859d 100644
--- a/third_party/WebKit/Source/core/loader/FrameLoaderTypes.h
+++ b/third_party/WebKit/Source/core/loader/FrameLoaderTypes.h
@@ -32,14 +32,17 @@
 namespace blink {
 
 // See WebFrameLoadType in public/web/WebFrameLoadType.h for details.
+// These values are used for UMA histogram. New enum values can be added, but
+// existing enums must never be renumbered or deleted and reused.

[Nate Chapin, 2017/06/14 18:10:50]

Please don't use this enum directly for UMAs. It's very much an implementation
detail of blink, and I'd appreciate the flexibility to reuse or merge values
without worrying about numerical consistency.

[Liquan (Max) Gu, 2017/06/20 23:35:39]

Done.

 enum FrameLoadType {
-  kFrameLoadTypeStandard,
-  kFrameLoadTypeBackForward,
-  kFrameLoadTypeReload,
-  kFrameLoadTypeReplaceCurrentItem,
-  kFrameLoadTypeInitialInChildFrame,
-  kFrameLoadTypeInitialHistoryLoad,
-  kFrameLoadTypeReloadBypassingCache,
+  kFrameLoadTypeStandard = 0,
+  kFrameLoadTypeBackForward = 1,
+  kFrameLoadTypeReload = 2,
+  kFrameLoadTypeReplaceCurrentItem = 3,
+  kFrameLoadTypeInitialInChildFrame = 4,
+  kFrameLoadTypeInitialHistoryLoad = 5,
+  kFrameLoadTypeReloadBypassingCache = 6,
+  kFrameLoadTypeCount = kFrameLoadTypeReloadBypassingCache
 };
 
 enum NavigationType {