Bug 1674968 - Fix UniqueJSONStrings copy constructor, to actually copy from the source - r=gregtatum

Differential Revision: https://phabricator.services.mozilla.com/D95833

mozglue/baseprofiler/core/ProfileJSONWriter.cpp

@@ -15,7 +15,7 @@ UniqueJSONStrings::UniqueJSONStrings(JSONWriter::CollectionStyle aStyle) {
 UniqueJSONStrings::UniqueJSONStrings(const UniqueJSONStrings& aOther,
                                      JSONWriter::CollectionStyle aStyle) {
   mStringTableWriter.StartBareList(aStyle);
-  uint32_t count = mStringHashToIndexMap.count();
+  uint32_t count = aOther.mStringHashToIndexMap.count();
   if (count != 0) {
     MOZ_RELEASE_ASSERT(mStringHashToIndexMap.reserve(count));
     for (auto iter = aOther.mStringHashToIndexMap.iter(); !iter.done();

mozglue/tests/TestBaseProfiler.cpp

@@ -3719,9 +3719,6 @@ void TestUniqueJSONStrings() {
         "2, 3, 2", R"("external0", "external1", "string0", "string1")", &ujs);
   }
 
-// This currently fails, demonstrating the regression from bug 1520104, to be
-// fixed in the next patch in bug 1674968.
-#  if 0
   // Unique string table with pre-existing data from another table.
   {
     UJS ujs(mozilla::JSONWriter::SingleLineStyle);
@@ -3740,7 +3737,6 @@ void TestUniqueJSONStrings() {
         },
         "2, 3, 2", R"("external0", "external1", "string0", "string1")", &ujs);
   }
-#  endif
 
   printf("TestUniqueJSONStrings done\n");
 }