Fix text missing in performance overlay (on Android)

flow/layers/performance_overlay_layer.cc

@@ -76,10 +76,19 @@ sk_sp<SkTextBlob> PerformanceOverlayLayer::MakeStatisticsText(
   SkFont font;
   sk_sp<SkFontMgr> font_mgr = txt::GetDefaultFontManager();
   if (font_path == "") {
-    font = SkFont(font_mgr->matchFamilyStyle(nullptr, {}), 15);
+    if (sk_sp<SkTypeface> face = font_mgr->matchFamilyStyle(nullptr, {})) {
+      font = SkFont(face, 15);
+    } else {
+      // In Skia's Android fontmgr, matchFamilyStyle can return null instead
+      // of falling back to a default typeface. If that's the case, we can use
+      // legacyMakeTypeface, which *does* use that default typeface.
+      font = SkFont(font_mgr->legacyMakeTypeface(nullptr, {}), 15);
+    }
   } else {
     font = SkFont(font_mgr->makeFromFile(font_path.c_str()), 15);
   }
+  // Make sure there's not an empty typeface returned, or we won't see any text.
+  FML_DCHECK(font.getTypeface()->countGlyphs() > 0);
 
   double max_ms_per_frame = stopwatch.MaxDelta().ToMillisecondsF();
   double average_ms_per_frame = stopwatch.AverageDelta().ToMillisecondsF();