Remove only-in-tests null checks in SkyframeActionExecutor.

Still on step -0.5, let's be honest.

--
PiperOrigin-RevId: 150783638
MOS_MIGRATED_REVID=150783638
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java
index 1396334..7c353ac 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java
@@ -131,8 +131,10 @@
   private boolean keepGoing;
   private boolean hadExecutionError;
   private ActionInputFileCache perBuildFileCache;
+  /** These variables are nulled out between executions. */
   private ProgressSupplier progressSupplier;
   private ActionCompletedReceiver completionReceiver;
+
   private final AtomicReference<ActionExecutionStatusReporter> statusReporterRef;
   private OutputService outputService;
 
@@ -393,9 +395,7 @@
         // Tell the receiver that the action has completed *before* telling the reporter.
         // This way the latter will correctly show the number of completed actions when task
         // completion messages are enabled (--show_task_finish).
-        if (completionReceiver != null) {
-          completionReceiver.actionCompleted(action);
-        }
+        completionReceiver.actionCompleted(action);
         reporter.finishTask(null, prependExecPhaseStats(message));
       }
     }
@@ -658,14 +658,9 @@
   }
 
   private String prependExecPhaseStats(String message) {
-    if (progressSupplier != null) {
-      // Prints a progress message like:
-      //   [2608/6445] Compiling foo/bar.cc [host]
-      return progressSupplier.getProgressString() + " " + message;
-    } else {
-      // progressSupplier may be null in tests
-      return message;
-    }
+    // Prints a progress message like:
+    //   [2608/6445] Compiling foo/bar.cc [host]
+    return progressSupplier.getProgressString() + " " + message;
   }
 
   /**
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java
index 75dcc14..76667a3 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ParallelBuilderTest.java
@@ -775,12 +775,12 @@
     buildArtifacts(baz);
     // Check that the percentages increase non-linearly, because foo has 10 input files
     List<String> expectedMessages = Lists.newArrayList(
-        "Test foo START",
-        "Test foo FINISH",
-        "Test bar START",
-        "Test bar FINISH",
-        "Test baz START",
-        "Test baz FINISH");
+        " Test foo START",
+        " Test foo FINISH",
+        " Test bar START",
+        " Test bar FINISH",
+        " Test baz START",
+        " Test baz FINISH");
     assertThat(messages).containsAllIn(expectedMessages);
 
     // Now do an incremental rebuild of bar and baz,
@@ -792,10 +792,10 @@
     // (in-memory) file system, rather than using cached entries.
     buildArtifacts(baz);
     expectedMessages = Lists.newArrayList(
-        "Test bar START",
-        "Test bar FINISH",
-        "Test baz START",
-        "Test baz FINISH");
+        " Test bar START",
+        " Test bar FINISH",
+        " Test baz START",
+        " Test baz FINISH");
     assertThat(messages).containsAllIn(expectedMessages);
   }
 }
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java b/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java
index 46932ea..2ca64ea 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java
@@ -53,6 +53,8 @@
 import com.google.devtools.build.lib.skyframe.ExternalFilesHelper.ExternalFileAction;
 import com.google.devtools.build.lib.skyframe.PackageLookupFunction.CrossRepositoryLabelViolationStrategy;
 import com.google.devtools.build.lib.skyframe.PackageLookupValue.BuildFileName;
+import com.google.devtools.build.lib.skyframe.SkyframeActionExecutor.ActionCompletedReceiver;
+import com.google.devtools.build.lib.skyframe.SkyframeActionExecutor.ProgressSupplier;
 import com.google.devtools.build.lib.testutil.FoundationTestCase;
 import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.testutil.TestRuleClassProvider;
@@ -242,6 +244,8 @@
             false,
             new ActionCacheChecker(actionCache, null, ALWAYS_EXECUTE_FILTER, null),
             null);
+        skyframeActionExecutor.setActionExecutionProgressReportingObjects(
+            EMPTY_PROGRESS_SUPPLIER, EMPTY_COMPLETION_RECEIVER);
 
         List<SkyKey> keys = new ArrayList<>();
         for (Artifact artifact : artifacts) {
@@ -461,4 +465,18 @@
       return actionTemplateExpansionFunction.extractTag(skyKey);
     }
   }
+
+  private static final ProgressSupplier EMPTY_PROGRESS_SUPPLIER =
+      new ProgressSupplier() {
+        @Override
+        public String getProgressString() {
+          return "";
+        }
+      };
+
+  private static final ActionCompletedReceiver EMPTY_COMPLETION_RECEIVER =
+      new ActionCompletedReceiver() {
+        @Override
+        public void actionCompleted(Action action) {}
+      };
 }