Prevent infinite loop about itemizing text in RenderTextHarfBuzz.

ui/gfx/render_text_unittest.cc

Index: ui/gfx/render_text_unittest.cc
diff --git a/ui/gfx/render_text_unittest.cc b/ui/gfx/render_text_unittest.cc
index 42825579ec6cb0b68fe701de431a2c1444d5c1f7..0d776ae7edfa1c76577f9ef32328f56afc1e787e 100644
--- a/ui/gfx/render_text_unittest.cc
+++ b/ui/gfx/render_text_unittest.cc
@@ -2577,6 +2577,16 @@ TEST_F(RenderTextTest, HarfBuzz_EmptyRun) {
   EXPECT_EQ(Range(0, 0), glyphs);
 }
 
+// Ensures RenderTextHarfBuzz::ItemizeTextToRuns() does not enter into an
+// infinite loop. See crbug.com/403892.
+TEST_F(RenderTextTest, HarfBuzz_InfiniteLoop) {
+  RenderTextHarfBuzz render_text;
+  render_text.SetObscured(true);
+  render_text.SetText(UTF8ToUTF16("\xF0\x9F\x98\x81y"));
+  gfx::Canvas canvas;
+  render_text.Draw(&canvas);
+}
+
 // Ensure a string fits in a display rect with a width equal to the string's.
 TEST_F(RenderTextTest, StringFitsOwnWidth) {
   scoped_ptr<RenderText> render_text(RenderText::CreateInstance());