data_resource_helper: use String::FromUTF8 overload that takes base::StringPiece.

This avoids an unnecessary strlen (the length is already known) and would also fix
the result for any hypothetical resource that had a null character inside it, which
is legal (though it's somewhat doubtful that we have any such resource).

Change-Id: I2a75d1a058d6980076bdc33467fd1c50c7b19591
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1741290
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Auto-Submit: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#685202}

third_party/blink/renderer/platform/data_resource_helper.cc

@@ -32,7 +32,7 @@ String UncompressResourceAsString(int resource_id) {
   ui::ResourceBundle& bundle = ui::ResourceBundle::GetSharedInstance();
   std::string uncompressed = bundle.DecompressDataResourceScaled(
       resource_id, bundle.GetMaxScaleFactor());
-  return String::FromUTF8(uncompressed.data());
+  return String::FromUTF8(uncompressed);
 }
 
 Vector<char> UncompressResourceAsBinary(int resource_id) {