Don't reuse removed NotRestoredReason::kFrameTreeNodeStateReset value

The kFrameTreeNodeStateReset value was removed in crrev.com/c/2536467,
and the value (36) was later on incorrectly reused for a different
NotRestoredReason, kNavigationCancelledWhileRestoring. This CL changes
the value for kNavigationCancelledWhileRestoring to 41 so that we
won't get confused on which reason was actually logged.

Change-Id: I776717c88a02920b429f1949048e3a0771aa17b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2592282Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837724}

content/browser/renderer_host/back_forward_cache_metrics.h

@@ -85,12 +85,13 @@ class BackForwardCacheMetrics
     // BackForwardCache is disabled due to command-line switch (may include
     // cases where the embedder disabled it due to, e.g., enterprise policy).
     kBackForwardCacheDisabledByCommandLine = 35,
-    kNavigationCancelledWhileRestoring = 36,
+    // 36: kFrameTreeNodeStateReset was removed.
     kNetworkRequestDatapipeDrained = 37,
     kNetworkRequestRedirected = 38,
     kNetworkRequestTimeout = 39,
     kNetworkExceedsBufferLimit = 40,
-    kMaxValue = kNetworkExceedsBufferLimit,
+    kNavigationCancelledWhileRestoring = 41,
+    kMaxValue = kNavigationCancelledWhileRestoring,
   };
 
   using NotRestoredReasons =

tools/metrics/histograms/enums.xml

@@ -6228,6 +6228,12 @@ others/histograms.xml -->
       label="BackForwardCache is disabled through command line (may include
              cases where the embedder disabled it due to, e.g., enterprise
              policy)"/>
+  <int value="36" label="kFrameTreeNodeStateReset (removed)"/>
+  <int value="37" label="Network request datapipe drained"/>
+  <int value="38" label="Network request redirected"/>
+  <int value="39" label="Network request timed out"/>
+  <int value="40" label="Network request exceeds buffer limit"/>
+  <int value="41" label="Navigation was cancelled while restoring"/>
 </enum>
 
 <enum name="BackForwardCacheReloadsAfterHistoryNavigation">