--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -1508,16 +1508,18 @@ nsBlockFrame::Reflow(nsPresContext*     
     char buf[400];
     SprintfLiteral(buf,
                    ": %" PRId64 " elapsed (%" PRId64 " per line) (%d lines; %d new lines)",
                    delta, perLineDelta, numLines, ectc - ctc);
     printf("%s\n", buf);
   }
 #endif
 
+  // Bug 1358299 START: Remove this code after the 56 merge date.
+
   // Bug 1351383: Collect data for the BOX_ALIGN_PROPS_IN_BLOCKS_FLAG probe.
   auto IsStyleNormal = [](uint16_t value)->bool {
     return (value == NS_STYLE_ALIGN_NORMAL);
   };
 
   // First check this frame for non-default values of the css-align properties
   // that apply to block containers.
   // Note: we check here for non-default "justify-items", though technically
@@ -1540,16 +1542,17 @@ nsBlockFrame::Reflow(nsPresContext*     
       if (line->IsBlock() &&
           !IsStyleNormal(line->mFirstChild->StylePosition()->mJustifySelf)) {
         Telemetry::Accumulate(
           Telemetry::BOX_ALIGN_PROPS_IN_BLOCKS_FLAG, true);
         break;
       }
     }
   }
+  // Bug 1358299 END
 
   NS_FRAME_SET_TRUNCATION(aStatus, (*reflowInput), aMetrics);
 }
 
 bool
 nsBlockFrame::CheckForCollapsedBEndMarginFromClearanceLine()
 {
   LineIterator begin = LinesBegin();