Upgrade OkHttp library to fix HTTP2 issue

Issue: #4078
PiperOrigin-RevId: 288651166

RELEASENOTES.md

@@ -49,6 +49,9 @@
   later).
 * Parse `text-combine-upright` CSS property (i.e. tate-chu-yoko) in WebVTT
   subtitles (rendering is coming later).
+* OkHttp extension: Upgrade OkHttp dependency to 3.12.7, which fixes a class of
+  `SocketTimeoutException` issues when using HTTP/2
+  ([#4078](https://github.com/google/ExoPlayer/issues/4078)).
 
 ### 2.11.1 (2019-12-20) ###
 

extensions/okhttp/build.gradle

@@ -41,7 +41,7 @@ dependencies {
     // https://cashapp.github.io/2019-02-05/okhttp-3-13-requires-android-5
     // Since OkHttp is distributed as a jar rather than an aar, Gradle won't
     // stop us from making this mistake!
-    api 'com.squareup.okhttp3:okhttp:3.12.5'
+    api 'com.squareup.okhttp3:okhttp:3.12.7'
 }
 
 ext {