Clean up extension READMEs

Issue: #1157

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=164434768

extensions/cronet/README.md

@@ -1,15 +1,13 @@
-# ExoPlayer Cronet Extension #
+# ExoPlayer Cronet extension #
 
 ## Description ##
 
-[Cronet][] is Chromium's Networking stack packaged as a library.
+The Cronet extension is an [HttpDataSource][] implementation using [Cronet][].
-
-The Cronet Extension is an [HttpDataSource][] implementation using [Cronet][].
 
 [HttpDataSource]: https://google.github.io/ExoPlayer/doc/reference/com/google/android/exoplayer/upstream/HttpDataSource.html
 [Cronet]: https://chromium.googlesource.com/chromium/src/+/master/components/cronet?autodive=0%2F%2F
 
-## Build Instructions ##
+## Build instructions ##
 
 To use this extension you need to clone the ExoPlayer repository and depend on
 its modules locally. Instructions for doing this can be found in ExoPlayer's
@@ -33,3 +31,28 @@ gradle.ext.exoplayerIncludeCronetExtension = true;
 
 [top level README]: https://github.com/google/ExoPlayer/blob/release-v2/README.md
 [here]: https://console.cloud.google.com/storage/browser/chromium-cronet/android
+
+## Using the extension ##
+
+ExoPlayer requests data through `DataSource` instances. These instances are
+either instantiated and injected from application code, or obtained from
+instances of `DataSource.Factory` that are instantiated and injected from
+application code.
+
+If your application only needs to play http(s) content, using the Cronet
+extension is as simple as updating any `DataSource`s and `DataSource.Factory`
+instantiations in your application code to use `CronetDataSource` and
+`CronetDataSourceFactory` respectively. If your application also needs to play
+non-http(s) content such as local files, use
+```
+new DefaultDataSource(
+    ...
+    new CronetDataSource(...) /* baseDataSource argument */);
+```
+and
+```
+new DefaultDataSourceFactory(
+    ...
+    new CronetDataSourceFactory(...) /* baseDataSourceFactory argument */);
+```
+respectively.

extensions/ffmpeg/README.md

@@ -1,4 +1,4 @@
-# FfmpegAudioRenderer #
+# ExoPlayer FFmpeg extension #
 
 ## Description ##
 

extensions/flac/README.md

@@ -1,14 +1,14 @@
-# ExoPlayer Flac Extension #
+# ExoPlayer Flac extension #
 
 ## Description ##
 
-The Flac Extension is a [Renderer][] implementation that helps you bundle
+The Flac extension is a [Renderer][] implementation that helps you bundle
 libFLAC (the Flac decoding library) into your app and use it along with
 ExoPlayer to play Flac audio on Android devices.
 
 [Renderer]: https://google.github.io/ExoPlayer/doc/reference/com/google/android/exoplayer2/Renderer.html
 
-## Build Instructions ##
+## Build instructions ##
 
 To use this extension you need to clone the ExoPlayer repository and depend on
 its modules locally. Instructions for doing this can be found in ExoPlayer's

extensions/gvr/README.md

@@ -1,4 +1,4 @@
-# ExoPlayer GVR Extension #
+# ExoPlayer GVR extension #
 
 ## Description ##
 

extensions/mediasession/README.md

@@ -1,8 +1,8 @@
-# ExoPlayer MediaSession Extension #
+# ExoPlayer MediaSession extension #
 
 ## Description ##
 
-The MediaSession Extension mediates between an ExoPlayer instance and a
+The MediaSession extension mediates between an ExoPlayer instance and a
 [MediaSession][]. It automatically retrieves and implements playback actions
 and syncs the player state with the state of the media session. The behaviour
 can be extended to support other playback and custom actions.

extensions/okhttp/README.md

@@ -1,8 +1,8 @@
-# ExoPlayer OkHttp Extension #
+# ExoPlayer OkHttp extension #
 
 ## Description ##
 
-The OkHttp Extension is an [HttpDataSource][] implementation using Square's
+The OkHttp extension is an [HttpDataSource][] implementation using Square's
 [OkHttp][].
 
 [HttpDataSource]: https://google.github.io/ExoPlayer/doc/reference/com/google/android/exoplayer2/upstream/HttpDataSource.html
@@ -24,3 +24,28 @@ locally. Instructions for doing this can be found in ExoPlayer's
 [top level README][].
 
 [top level README]: https://github.com/google/ExoPlayer/blob/release-v2/README.md
+
+## Using the extension ##
+
+ExoPlayer requests data through `DataSource` instances. These instances are
+either instantiated and injected from application code, or obtained from
+instances of `DataSource.Factory` that are instantiated and injected from
+application code.
+
+If your application only needs to play http(s) content, using the OkHttp
+extension is as simple as updating any `DataSource`s and `DataSource.Factory`
+instantiations in your application code to use `OkHttpDataSource` and
+`OkHttpDataSourceFactory` respectively. If your application also needs to play
+non-http(s) content such as local files, use
+```
+new DefaultDataSource(
+    ...
+    new OkHttpDataSource(...) /* baseDataSource argument */);
+```
+and
+```
+new DefaultDataSourceFactory(
+    ...
+    new OkHttpDataSourceFactory(...) /* baseDataSourceFactory argument */);
+```
+respectively.

extensions/opus/README.md

@@ -1,14 +1,14 @@
-# ExoPlayer Opus Extension #
+# ExoPlayer Opus extension #
 
 ## Description ##
 
-The Opus Extension is a [Renderer][] implementation that helps you bundle
+The Opus extension is a [Renderer][] implementation that helps you bundle
 libopus (the Opus decoding library) into your app and use it along with
 ExoPlayer to play Opus audio on Android devices.
 
 [Renderer]: https://google.github.io/ExoPlayer/doc/reference/com/google/android/exoplayer2/Renderer.html
 
-## Build Instructions ##
+## Build instructions ##
 
 To use this extension you need to clone the ExoPlayer repository and depend on
 its modules locally. Instructions for doing this can be found in ExoPlayer's

extensions/rtmp/README.md

@@ -1,8 +1,8 @@
-# ExoPlayer RTMP Extension #
+# ExoPlayer RTMP extension #
 
 ## Description ##
 
-The RTMP Extension is a [DataSource][] implementation for playing [RTMP][]
+The RTMP extension is a [DataSource][] implementation for playing [RTMP][]
 streams using [LibRtmp Client for Android][].
 
 [DataSource]: https://google.github.io/ExoPlayer/doc/reference/com/google/android/exoplayer2/upstream/DataSource.html

extensions/vp9/README.md

@@ -1,14 +1,14 @@
-# ExoPlayer VP9 Extension #
+# ExoPlayer VP9 extension #
 
 ## Description ##
 
-The VP9 Extension is a [Renderer][] implementation that helps you bundle libvpx
+The VP9 extension is a [Renderer][] implementation that helps you bundle libvpx
 (the VP9 decoding library) into your app and use it along with ExoPlayer to play
 VP9 video on Android devices.
 
 [Renderer]: https://google.github.io/ExoPlayer/doc/reference/com/google/android/exoplayer2/Renderer.html
 
-## Build Instructions ##
+## Build instructions ##
 
 To use this extension you need to clone the ExoPlayer repository and depend on
 its modules locally. Instructions for doing this can be found in ExoPlayer's