Calculate mailbox and channel test files as Test LOC stats

If they are not included in this "test types" list, they're counted
towards app code lines, not test lines.

railties/lib/rails/code_statistics.rb

@@ -8,6 +8,8 @@ class CodeStatistics #:nodoc:
                 "Helper tests",
                 "Model tests",
                 "Mailer tests",
+                "Mailbox tests",
+                "Channel tests",
                 "Job tests",
                 "Integration tests",
                 "System tests"]

railties/test/application/rake_test.rb

@@ -141,7 +141,7 @@ module ApplicationTests
     end
 
     def test_code_statistics_sanity
-      assert_match "Code LOC: 32     Test LOC: 0     Code to Test Ratio: 1:0.0",
+      assert_match "Code LOC: 29     Test LOC: 3     Code to Test Ratio: 1:0.1",
         rails("stats")
     end