Document load() exceptions

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=172329677

library/core/src/main/java/com/google/android/exoplayer2/upstream/Loader.java

@@ -61,8 +61,8 @@ public final class Loader implements LoaderErrorThrower {
     /**
      * Performs the load, returning on completion or cancellation.
      *
-     * @throws IOException
-     * @throws InterruptedException
+     * @throws IOException If the input could not be loaded.
+     * @throws InterruptedException If the thread was interrupted.
      */
     void load() throws IOException, InterruptedException;