Bug 1628954 - Don't use 'is' and 'is not' to perform comparison against strings in Python r=nalexander

Differential Revision: https://phabricator.services.mozilla.com/D71059

--HG--
extra : moz-landing-system : lando

Author: Ricky Stewart

dom/bindings/GenerateCSS2PropertiesWebIDL.py

@@ -23,7 +23,7 @@ def generate(output, idlFilename, dataFile):
         # (e.g. on nsComputedDOMStyle).
         extendedAttrs = ["CEReactions", "Throws",
                          "SetterNeedsSubjectPrincipal=NonSystem"]
-        if p.pref is not "":
+        if p.pref != "":
             extendedAttrs.append('Pref="%s"' % p.pref)
 
         prop = p.method

xpcom/ds/StaticAtoms.py

@@ -2582,11 +2582,11 @@ def generate_nsgkatomconsts_h(output, *ignore):
     pseudo_count = 0
     anon_box_count = 0
     for i, atom in enumerate(STATIC_ATOMS):
-        if atom.atom_type is "PseudoElementAtom":
+        if atom.atom_type == "PseudoElementAtom":
             if pseudo_index is None:
                 pseudo_index = i
             pseudo_count += 1
-        elif atom.atom_type is "NonInheritingAnonBoxAtom" or atom.atom_type is "InheritingAnonBoxAtom":
+        elif atom.atom_type == "NonInheritingAnonBoxAtom" or atom.atom_type == "InheritingAnonBoxAtom":
             if anon_box_index is None:
                 anon_box_index = i
             anon_box_count += 1