Allow blank titles as valid for "frame_title" field.

BUG=954850,1023844
R=mcasas, tmathmeyer

Change-Id: I0f224070ccc179a2219690f063301359ef0197ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1913575
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Ted Meyer <tmathmeyer@chromium.org>
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Ted Meyer <tmathmeyer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714763}

media/blink/webmediaplayer_impl.cc

@@ -263,9 +263,8 @@ void SetSanitizedStringProperty(MediaLog* log,
                                 std::string key,
                                 blink::WebString value) {
   std::string converted = value.Utf8();
-  if (converted.empty() || !base::IsStringUTF8(converted)) {
-    converted = "<invalid property>";
-  }
+  if (!base::IsStringUTF8(converted))
+    converted = "[invalid property]";
   log->SetStringProperty(key, converted);
 }