Refactoring: pull out the call to update buildResult.

Also remove the unnecessary state check.

--
MOS_MIGRATED_REVID=109396856
diff --git a/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java b/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
index b50317b..7e8795f 100644
--- a/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
+++ b/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
@@ -468,11 +468,11 @@
       }
 
       try (AutoProfiler p = AutoProfiler.profiled("Show results", ProfilerTask.INFO)) {
-        determineSuccessfulTargets(buildResult, configuredTargets, builtTargets, timer);
+        buildResult.setSuccessfulTargets(
+            determineSuccessfulTargets(configuredTargets, builtTargets, timer));
         BuildResultPrinter buildResultPrinter = new BuildResultPrinter(env);
         buildResultPrinter.showBuildResult(
             request, buildResult, configuredTargets, analysisResult.getAspects());
-        Preconditions.checkNotNull(buildResult.getSuccessfulTargets());
       }
 
       try (AutoProfiler p = AutoProfiler.profiled("Show artifacts", ProfilerTask.INFO)) {
@@ -633,7 +633,7 @@
    *                          built.
    * @param timer A timer that was started when the execution phase started.
    */
-  private void determineSuccessfulTargets(BuildResult result,
+  private Collection<ConfiguredTarget> determineSuccessfulTargets(
       Collection<ConfiguredTarget> configuredTargets, Set<ConfiguredTarget> builtTargets,
       Stopwatch timer) {
     // Maintain the ordering by copying builtTargets into a LinkedHashSet in the same iteration
@@ -646,7 +646,7 @@
     }
     env.getEventBus().post(
         new ExecutionPhaseCompleteEvent(timer.stop().elapsed(TimeUnit.MILLISECONDS)));
-    result.setSuccessfulTargets(successfulTargets);
+    return successfulTargets;
   }