Report frequency of single page app navigations to UMA

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

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 14 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef FrameLoaderTypes_h
 #define FrameLoaderTypes_h
 
 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 {
   kNavigationTypeLinkClicked,
   kNavigationTypeFormSubmitted,
   kNavigationTypeBackForward,
   kNavigationTypeReload,
   kNavigationTypeFormResubmitted,
   kNavigationTypeOther
 };
@@ skipping 44 matching lines @@
 enum class ProgressBarCompletion {
   kLoadEvent,
   kResourcesBeforeDCL,
   kDOMContentLoaded,
   kResourcesBeforeDCLAndSameOriginIFrames
 };
 
 }  // namespace blink
 
 #endif