code: void recordPassStop(String passName, long runtime) {
      int allocMem = getAllocatedMegabytes();
      Stats logStats = this.currentPass.pop();
      checkState(passName.equals(logStats.pass));
      this.log.add(logStats);
  
      // Update fields that aren't related to code size
      logStats.runtime = runtime;
      logStats.allocMem = allocMem;
      logStats.runs = 1;
      if (this.codeChange.hasCodeChanged()) {
        logStats.changes = 1;
      }
      if (passName.equals(PassNames.PARSE_INPUTS)) {
        recordParsingStop(logStats);
      } else if (this.codeChange.hasCodeChanged() && tracksAstSize()) {
        recordOtherPassStop(logStats);
      }
    }
docs: Collects information about a pass P after P finishes running, eg, how much
  time P took and what was its impact on code size.
  
  @param passName short name of the pass
  @param runtime execution time in milliseconds