Add initial Document::getAnnot support

testing/resources/javascript/document_methods.in

 {{header}}
 {{object 1 0}} <<
   /Type /Catalog
   /Pages 2 0 R
   /OpenAction 10 0 R
 >>
 endobj
 {{object 2 0}} <<
   /Type /Pages
   /Count 4
@@ skipping 117 matching lines @@
 }
 
 function testCalculateNow() {
    // Method is present.
    expect('typeof this.calculateNow', 'function');
 
    // TODO(tsepez): test with no permissions.
    // TODO(tsepez): test success cases.
 }
 
+function testGetAnnot() {
+   // Method is present.
+   expect('typeof this.getAnnot', 'function');
+
+   // Method needs two arguments.
+   expectError('this.getAnnot()');
+   expectError('this.getAnnot(0)');
+   expectError('this.getAnnot(0, "test", 0)');
+
+   // TODO(tonikitoo): test success cases.
+}
+
 function testGetField() {
    // Method is present.
    expect('typeof this.getField', 'function');
 
    // Method needs at least one argument.
    expectError('this.getField()');
 
    // TODO(tsepez): test success cases.
 }
 
@@ skipping 134 matching lines @@
   testUnsupported('this.addAnnot');
   testUnsupported('this.addField');
   testUnsupported('this.addLink');
   testUnsupported('this.closeDoc');
   testUnsupported('this.createDataObject');
   testUnsupported('this.deletePages');
   testUnsupported('this.exportAsFDF');
   testUnsupported('this.exportAsText');
   testUnsupported('this.exportAsXFDF');
   testUnsupported('this.extractPages');
-  testUnsupported('this.getAnnot');
   testUnsupported('this.getAnnot3D');
   testUnsupported('this.getAnnots');
   testUnsupported('this.getLinks');
   testUnsupported('this.getOCGs');
   testUnsupported('this.getPageBox');
   testUnsupported('this.getURL');
   testUnsupported('this.importAnFDF');
   testUnsupported('this.importAnXFDF');
   testUnsupported('this.importTextData');
   testUnsupported('this.insertPages');
   testUnsupported('this.removeIcon');
   testUnsupported('this.replacePages');
   testUnsupported('this.saveAs');
 
   app.alert('*** Testing Supported Methods ***');
   testAddIcon();
   testCalculateNow();
+  testGetAnnot();
   testGetField();
   testGetIcon();
   testGetNthFieldName();
   testGetPageNthWord();
   testGetPageNthWordQuads();
   testGetPageNumWords();
   testGetPrintParams();
   testGotoNamedDest();
   testMailDoc();
   testMailForm();
   testPrint();
   testRemoveField();
   testResetForm();
   testSubmitForm();
 } catch (e) {
   app.alert('FATAL: ' + e.toString());
 }
 endstream
 endobj
 {{xref}}
 trailer <<
   /Root 1 0 R
   /Info 9 0 R
 >>
 {{startxref}}
 %%EOF