Widget annotations: simplify field flag handling

Directly use the hexadecimal representation, just like the
`AnnotationFlags`, to avoid calculations and to improve readability.
This allows us to simplify the unit tests for text widget annotations as
well.

src/shared/util.js

@@ -94,25 +94,25 @@ var AnnotationFlag = {
 };
 
 var AnnotationFieldFlag = {
-  READONLY: 1,
-  REQUIRED: 2,
-  NOEXPORT: 3,
-  MULTILINE: 13,
-  PASSWORD: 14,
-  NOTOGGLETOOFF: 15,
-  RADIO: 16,
-  PUSHBUTTON: 17,
-  COMBO: 18,
-  EDIT: 19,
-  SORT: 20,
-  FILESELECT: 21,
-  MULTISELECT: 22,
-  DONOTSPELLCHECK: 23,
-  DONOTSCROLL: 24,
-  COMB: 25,
-  RICHTEXT: 26,
-  RADIOSINUNISON: 26,
-  COMMITONSELCHANGE: 27,
+  READONLY: 0x0000001,
+  REQUIRED: 0x0000002,
+  NOEXPORT: 0x0000004,
+  MULTILINE: 0x0001000,
+  PASSWORD: 0x0002000,
+  NOTOGGLETOOFF: 0x0004000,
+  RADIO: 0x0008000,
+  PUSHBUTTON: 0x0010000,
+  COMBO: 0x0020000,
+  EDIT: 0x0040000,
+  SORT: 0x0080000,
+  FILESELECT: 0x0100000,
+  MULTISELECT: 0x0200000,
+  DONOTSPELLCHECK: 0x0400000,
+  DONOTSCROLL: 0x0800000,
+  COMB: 0x1000000,
+  RICHTEXT: 0x2000000,
+  RADIOSINUNISON: 0x2000000,
+  COMMITONSELCHANGE: 0x4000000,
 };
 
 var AnnotationBorderStyleType = {