Rename ActionExitCode to ErrorCode

Nowadays ActionExitCode is used throughout the codebase so use a more
generic name to reflect this.

BUG=chromium:216507
TEST=unit tests pass

Change-Id: I23d1d7e2676443251dbc42ed137fd018aadfa8a3
Reviewed-on: https://gerrit.chromium.org/gerrit/49512
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: David Zeuthen <zeuthen@chromium.org>
Tested-by: David Zeuthen <zeuthen@chromium.org>
diff --git a/action_unittest.cc b/action_unittest.cc
index af0e130..e09967f 100644
--- a/action_unittest.cc
+++ b/action_unittest.cc
@@ -33,7 +33,7 @@
   void PerformAction() {}
   void CompleteAction() {
     ASSERT_TRUE(processor());
-    processor()->ActionComplete(this, kActionCodeSuccess);
+    processor()->ActionComplete(this, kErrorCodeSuccess);
   }
   string Type() const { return "ActionTestAction"; }
 };