Bug 1467759 - Escape all the property names in JSONWriter. r=froydnj

Scalar property names (e.g. IntProperty) are already escaped correctly.
This patch escapes the collection property names (e.g. StartObjectProperty)
as well (and adds test coverage for it).

MozReview-Commit-ID: 68kkjPb2ZN7

--HG--
extra : rebase_source : b42939ccebb71fc73914ff595803b2d6c7df2715

mfbt/JSONWriter.h

@@ -313,9 +313,7 @@ protected:
   {
     Separator();
     if (aMaybePropertyName) {
-      mWriter->Write("\"");
-      mWriter->Write(aMaybePropertyName);
-      mWriter->Write("\": ");
+      PropertyNameAndColon(aMaybePropertyName);
     }
     mWriter->Write(aStartChar);
     mNeedComma[mDepth] = true;

mfbt/tests/TestJSONWriter.cpp

@@ -527,6 +527,47 @@ void TestDeepNesting()
   Check(w.WriteFunc(), expected);
 }
 
+void TestEscapedPropertyNames()
+{
+  const char* expected = "\
+{\"i\\t\": 1, \"array\\t\": [null, [{}], {\"o\\t\": {}}, \"s\"], \"d\\t\": 3.33}\n\
+";
+
+  JSONWriter w(MakeUnique<StringWriteFunc>());
+
+  w.Start(w.SingleLineStyle);
+
+  w.IntProperty("i\t", 1);
+
+  w.StartArrayProperty("array\t");
+  {
+    w.NullElement();
+
+    w.StartArrayElement(w.MultiLineStyle);  // style overridden from above
+    {
+      w.StartObjectElement();
+      w.EndObject();
+    }
+    w.EndArray();
+
+    w.StartObjectElement();
+    {
+      w.StartObjectProperty("o\t");
+      w.EndObject();
+    }
+    w.EndObject();
+
+    w.StringElement("s");
+  }
+  w.EndArray();
+
+  w.DoubleProperty("d\t", 3.33);
+
+  w.End();
+
+  Check(w.WriteFunc(), expected);
+}
+
 int main(void)
 {
   TestBasicProperties();
@@ -534,6 +575,7 @@ int main(void)
   TestOneLineObject();
   TestStringEscaping();
   TestDeepNesting();
+  TestEscapedPropertyNames();
 
   return 0;
 }