XFA - Remove empty pages

- it aims to fix #13583;
  - fix the switch to breakBefore target;
  - force the layout of an unsplittable element on an empty page;
  - don't fail when there is horizontal overflow (except in lr-tb);
  - handle correctly overflow in the same content area (bug 1717805, bug 1717668);
  - fix a typo in radial gradient first argument.

test/pdfs/xfa_bug1717668_1.pdf.link

@@ -0,0 +1 @@
+https://bugzilla.mozilla.org/attachment.cgi?id=9228387

test/pdfs/xfa_bug1717668_2.pdf.link

@@ -0,0 +1 @@
+https://bugzilla.mozilla.org/attachment.cgi?id=9228727

test/pdfs/xfa_bug1717668_3.pdf.link

@@ -0,0 +1 @@
+https://bugzilla.mozilla.org/attachment.cgi?id=9228728

test/pdfs/xfa_bug1717805.pdf.link

@@ -0,0 +1 @@
+https://bugzilla.mozilla.org/attachment.cgi?id=9228507

test/pdfs/xfa_dhl_shipment.pdf.link

@@ -0,0 +1 @@
+https://web.archive.org/web/20210621073147/https://www.dhl.com/content/dam/downloads/g0/express/emailship_page/globalpage/dhl_emailship_pdfclient_my_en.pdf

test/pdfs/xfa_issue13611.pdf.link

@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/6695365/2229E.pdf

test/test_manifest.json

@@ -946,6 +946,38 @@
        "enableXfa": true,
        "type": "eq"
     },
+    {  "id": "xfa_bug1717805",
+       "file": "pdfs/xfa_bug1717805.pdf",
+       "md5": "c68ccebd0d92b8fd70c465660458507f",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
+    {  "id": "xfa_bug17176688_1",
+       "file": "pdfs/xfa_bug1717668_1.pdf",
+       "md5": "564ecff67be690b43c2a144ae5967034",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
+    {  "id": "xfa_bug17176688_2",
+       "file": "pdfs/xfa_bug1717668_2.pdf",
+       "md5": "08aa8bf9fec5aa7b8ff13d9ba72ca8ac",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
+    {  "id": "xfa_bug17176688_3",
+       "file": "pdfs/xfa_bug1717668_3.pdf",
+       "md5": "4ff2531dbefebabc3f128d4ae20552a4",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
     {  "id": "xfa_bug1718037",
        "file": "pdfs/xfa_bug1718037.pdf",
        "md5": "a0b53d50e9faed9d57950a5159d5da12",
@@ -970,6 +1002,14 @@
        "enableXfa": true,
        "type": "eq"
     },
+    {  "id": "xfa_dhl_shipment",
+       "file": "pdfs/xfa_dhl_shipment.pdf",
+       "md5": "503ece429d69e7d626d6932a475fbe63",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
     {  "id": "xfa_bug1716047",
        "file": "pdfs/xfa_bug1716047.pdf",
        "md5": "2f524163bd8397f43d195090978c3b56",
@@ -1050,6 +1090,14 @@
        "enableXfa": true,
        "type": "eq"
     },
+    {  "id": "xfa_issue13611",
+       "file": "pdfs/xfa_issue13611.pdf",
+       "md5": "e713fb46a6b4637660010f1850559ff6",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
     {  "id": "xfa_issue13634",
        "file": "pdfs/xfa_issue13634.pdf",
        "md5": "459a04045470811cbab6671772929d3d",

test/unit/xfa_tohtml_spec.js

@@ -56,14 +56,18 @@ describe("XFAFactory", function () {
           </draw>
         </pageArea>
       </pageSet>
-      <subform name="first">
-      </subform>
       <subform name="second">
         <breakBefore targetType="pageArea" startNew="1"/>
         <subform>
           <draw w="1pt" h="1pt"><value><text>foo</text></value></draw>
         </subform>
       </subform>
+      <subform name="third">
+        <breakBefore targetType="pageArea" startNew="1"/>
+        <subform>
+          <draw w="1pt" h="1pt"><value><text>bar</text></value></draw>
+        </subform>
+      </subform>
     </subform>
   </template>
   <xfa:datasets xmlns:xfa="http://www.xfa.org/schema/xfa-data/1.0/">
@@ -92,7 +96,6 @@ describe("XFAFactory", function () {
         width: "456px",
         left: "123px",
         top: "0px",
-        position: "absolute",
       });
 
       const wrapper = page1.children[0];