Put additional Javadoc files under src

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=127811486

library/build.gradle

@@ -77,6 +77,12 @@ android.libraryVariants.all { variant ->
         }
         exclude '**/BuildConfig.java'
         exclude '**/R.java'
+        doLast {
+            copy {
+                from "src/main/javadoc"
+                into "$buildDir/docs/javadoc"
+            }
+        }
     }
 }
 

library/src/main/java/com/google/android/exoplayer2/ExoPlayer.java

@@ -54,7 +54,7 @@ import com.google.android.exoplayer2.source.MediaSource;
  * <h3>Threading model</h3>
  *
  * <p>The figure below shows the {@link ExoPlayer} threading model.</p>
- * <p align="center"><img src="../../../../../images/exoplayer_threading_model.png"
+ * <p align="center"><img src="doc-files/exoplayer-threading-model.png"
  *     alt="MediaPlayer state diagram"
  *     border="0"/></p>
  *
@@ -82,14 +82,14 @@ import com.google.android.exoplayer2.source.MediaSource;
  * calling {@link #getPlaybackState()} is only ever changed as a result of operations completing on
  * the playback thread, as illustrated below.</p>
  *
- * <p align="center"><img src="../../../../../images/exoplayer_state.png"
+ * <p align="center"><img src="doc-files/exoplayer-state.png"
  *     alt="ExoPlayer state"
  *     border="0"/></p>
  *
  * <p>The possible playback state transitions are shown below. Transitions can be triggered either
  * by changes in the state of the {@link Renderer}s being used, or as a result of
  * {@link #setMediaSource(MediaSource)}, {@link #stop()} or {@link #release()} being invoked.</p>
- * <p align="center"><img src="../../../../../images/exoplayer_playbackstate.png"
+ * <p align="center"><img src="doc-files/exoplayer-playbackstate.png"
  *     alt="ExoPlayer playback state transitions"
  *     border="0"/></p>
  */

library/src/main/java/com/google/android/exoplayer2/Renderer.java

@@ -28,7 +28,7 @@ import java.io.IOException;
  * transition its renderers through various states as the overall playback state changes. The valid
  * state transitions are shown below, annotated with the methods that are invoked during each
  * transition.
- * <p align="center"><img src="../../../../../images/trackrenderer_state.png"
+ * <p align="center"><img src="doc-files/renderer-states.png"
  *     alt="Renderer state transitions"
  *     border="0"/></p>
  */