Roll engine 4893b07..715b64e (7 commits)

flutter/engine@4893b07...715b64e

git log 4893b07..715b64e --date=short --no-merges --format='%%ad %%ae %%s'
2018-08-03 37626415+[email protected] Roll src/third_party/skia 1400d38e0863..cdfa16d086b8 (10 commits) (flutter/engine#5934)
2018-08-03 [email protected] Flush all embedded Android views on hot restart. (flutter/engine#5929)
2018-08-03 37626415+[email protected] Roll src/third_party/skia 578ef2847b72..1400d38e0863 (7 commits) (flutter/engine#5933)
2018-08-02 [email protected] Don't drop MotionEvents with unknown tool type. (flutter/engine#5931)
2018-08-02 37626415+[email protected] Roll src/third_party/skia 64cc576b1fa7..578ef2847b72 (20 commits) (flutter/engine#5930)
2018-08-02 [email protected] Roll Dart to b04def964c428ada007cca7ef6b4936001db965d (flutter/engine#5928)
2018-08-02 [email protected] Add an explicit `-[FlutterViewController init]` implementation (flutter/engine#5924)

The AutoRoll server is located here: https://flutter-engine-flutter-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

Author: engine-flutter-autoroll

bin/internal/engine.version

@@ -1 +1 @@
-4893b0760df08cecd8ee97bdf03856c296a6df14
+715b64ee3a6a3d2feeee9d6a39b15ab76736ae8b