tests: Add avm2/edittext_getcharboundaries_missing_embedded_font test

This test verifies how getCharBoundaries() works when glyphs are missing
due to embedded font not being present.

tests/tests/swfs/avm2/edittext_getcharboundaries_missing_embedded_font/Test.as

@@ -0,0 +1,41 @@
+package {
+import flash.display.Sprite;
+import flash.text.TextField;
+import flash.text.TextFormat;
+
+[SWF(width="400", height="400")]
+public class Test extends Sprite {
+    private var text:TextField;
+
+    public function Test() {
+        stage.scaleMode = "noScale";
+        text = new TextField();
+        text.border = true;
+        text.x = 10;
+        text.y = 10;
+        text.width = 380;
+        text.height = 380;
+        text.multiline = true;
+        text.embedFonts = true;
+        addChild(text);
+
+        testHtml("<font face='Unknown Font'>x y</font>");
+    }
+
+    private function testHtml(htmlText:String):void {
+        text.htmlText = htmlText;
+        trace("Text: " + htmlText.replace(/[\r\n]/g, "\\n"));
+
+        testAt(-5);
+        testAt(-1);
+        for (var i = 0; i <= text.text.length; ++i) {
+            testAt(i);
+        }
+    }
+
+    private function testAt(charIndex:int):void {
+        var bounds = text.getCharBoundaries(charIndex);
+        trace("  text.getCharBoundaries(" + charIndex + ") = " + bounds);
+    }
+}
+}

tests/tests/swfs/avm2/edittext_getcharboundaries_missing_embedded_font/output.txt

@@ -0,0 +1,7 @@
+Text: <font face='Unknown Font'>x y</font>
+  text.getCharBoundaries(-5) = null
+  text.getCharBoundaries(-1) = null
+  text.getCharBoundaries(0) = null
+  text.getCharBoundaries(1) = null
+  text.getCharBoundaries(2) = null
+  text.getCharBoundaries(3) = null

tests/tests/swfs/avm2/edittext_getcharboundaries_missing_embedded_font/test.toml

@@ -0,0 +1,4 @@
+num_ticks = 1
+
+# Currently Ruffle falls back to device font on missing embedded font.
+known_failure = true