Avoid accessing empty SkData when retrieving matched font blob

When attempting to match a font from Android downloadable fonts, there
is a scenario in which no font can be created from the returned file
descriptor. Check for null SkData before testing for isEmpty()

Bug: 1127513
Change-Id: Icaa8e6fadfca6750e9eccb78e6d20c5de20c7f02
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2429272Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811228}

third_party/blink/renderer/platform/fonts/android/font_unique_name_lookup_android.cc

@@ -186,7 +186,7 @@ FontUniqueNameLookupAndroid::MatchUniqueNameFromDownloadableFonts(
 
   sk_sp<SkData> font_data = SkData::MakeFromFD(font_file.GetPlatformFile());
 
-  if (font_data->isEmpty()) {
+  if (!font_data || font_data->isEmpty()) {
     LOG(ERROR) << "Received file descriptor has 0 size.";
     lookup_latency_histogram_failure.CountMicroseconds(elapsed_timer.Elapsed());
     return nullptr;