Revert commits 5 and 6
Revert commits 5 and 6

After discussion on IRC with Ms2ger.  This was creating test output for me like

  assert_approx_equals: Value of X part (actual: \"40px 15px\", expected:
  \"50px 25px\") expected 50 +/- 0.05 but got 40

with undesired backslashes.  I suggested that he use format_value() himself
when constructing test names if they might contain bad characters.

hallvors/testharness.js,RatneshThakur/testharness.js,ayg/testharness.js,jyasskin/testharness.js,jyasskin/testharness.js,zqzhang/testharness.js,bboyle/testharness.js,hallvors/testharness.js