Refactor Histogram relationship diagnostics.

tracing/tracing/value/diagnostics/diagnostic_map.html

Index: tracing/tracing/value/diagnostics/diagnostic_map.html
diff --git a/tracing/tracing/value/diagnostics/diagnostic_map.html b/tracing/tracing/value/diagnostics/diagnostic_map.html
index 950d0e31dff9df5bceb5da0a25af83057e856248..4c69a2e858299762dd295ccd32f057b4853d5343 100644
--- a/tracing/tracing/value/diagnostics/diagnostic_map.html
+++ b/tracing/tracing/value/diagnostics/diagnostic_map.html
@@ -113,7 +113,8 @@ tr.exportTo('tr.v.d', function() {
 
     static fromObject(obj) {
       const diagnostics = new DiagnosticMap();
-      for (const [name, diagnostic] of Object.entries(obj)) {
+      if (!(obj instanceof Map)) obj = Object.entries(obj);
+      for (const [name, diagnostic] of obj) {
         diagnostics.set(name, diagnostic);
       }
       return diagnostics;
@@ -121,9 +122,7 @@ tr.exportTo('tr.v.d', function() {
 
     addDiagnostics(other) {
       for (const [name, otherDiagnostic] of other) {
-        if (name === tr.v.d.RESERVED_NAMES.MERGED_FROM ||
-            name === tr.v.d.RESERVED_NAMES.MERGED_TO ||
-            name === tr.v.d.RESERVED_NAMES.GROUPING_PATH) {
+        if (name === tr.v.d.RESERVED_NAMES.GROUPING_PATH) {
           continue;
         }
 
@@ -164,35 +163,6 @@ tr.exportTo('tr.v.d', function() {
               [myDiagnostic, clone]));
       }
     }
-
-    /**
-     * RelatedHistogram diagnostics cannot be merged when Histograms are merged
-     * because the related Histograms might not exist yet.
-     * This method assumes that all related Histograms exist and that duplicate
-     * Diagnostics have been deduplicated.
-     *
-     * @param {!tr.v.Histogram} parentHist
-     */
-    mergeRelationships(parentHist) {
-      for (const [name, diagnostic] of this) {
-        if (!(diagnostic instanceof tr.v.d.RelatedHistogramMap) &&
-            !(diagnostic instanceof tr.v.d.RelatedHistogramBreakdown) &&
-            !(diagnostic instanceof tr.v.d.UnmergeableDiagnosticSet)) {
-          continue;
-        }
-
-        for (const [unusedName, otherHist] of
-            this.get(tr.v.d.RESERVED_NAMES.MERGED_FROM)) {
-          const otherDiagnostic = otherHist.diagnostics.get(name);
-          if (!(otherDiagnostic instanceof tr.v.d.RelatedHistogramMap) &&
-              !(otherDiagnostic instanceof tr.v.d.RelatedHistogramBreakdown) &&
-              !(otherDiagnostic instanceof tr.v.d.UnmergeableDiagnosticSet)) {
-            continue;
-          }
-          diagnostic.mergeRelationships(otherDiagnostic, parentHist, otherHist);
-        }
-      }
-    }
   }
 
   return {