Ensure Firefox frame table subcategory fields are always included

Author: joshuay03

lib/vernier/output/firefox.rb

@@ -497,7 +497,7 @@ def frame_table
             address: [-1] * size,
             inlineDepth: [0] * size,
             category: categories,
-            subcategory: nil,
+            subcategory: none,
             func: funcs,
             nativeSymbol: none,
             innerWindowID: none,

test/firefox_test_helpers.rb

@@ -62,6 +62,8 @@ def assert_valid_firefox_profile(profile)
       assert_equal frame_length, thread["frameTable"]["innerWindowID"].length
       assert_equal frame_length, thread["frameTable"]["func"].length
       assert_equal frame_length, thread["frameTable"]["category"].length
+      assert_equal frame_length, thread["frameTable"]["subcategory"].length
+      assert_equal [], thread["frameTable"]["subcategory"].compact
       assert_equal frame_length, thread["frameTable"]["inlineDepth"].length
       assert_equal frame_length, thread["frameTable"]["address"].length