Add JobDispatcherScheduler

This is a Scheduler implementation which uses Firebase JobDispatcher.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=182051350

extensions/leanback/build.gradle

@@ -30,7 +30,7 @@ dependencies {
 }
 
 ext {
-    javadocTitle = 'Leanback extension for Exoplayer library'
+    javadocTitle = 'Leanback extension'
 }
 apply from: '../../javadoc_library.gradle'