Keeping CastOptionsProvider to avoid crash.

Bug: 1157603
Change-Id: I04bf94d2e2d758cd871d5328513de135c2e155de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2585843Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Commit-Queue: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836743}

components/media_router/browser/android/BUILD.gn

@@ -77,6 +77,7 @@ android_library("cast_options_provider_java") {
   deps = [
     "$google_play_services_package:google_play_services_cast_framework_java",
     "$google_play_services_package:google_play_services_cast_java",
+    "//base:base_java",
   ]
 }
 

components/media_router/browser/android/java/src/org/chromium/components/media_router/caf/CastOptionsProvider.java

@@ -11,9 +11,12 @@ import com.google.android.gms.cast.framework.CastOptions;
 import com.google.android.gms.cast.framework.OptionsProvider;
 import com.google.android.gms.cast.framework.SessionProvider;
 
+import org.chromium.base.annotations.UsedByReflection;
+
 import java.util.List;
 
 /** {@link OptionsProvider} implementation for Chrome MR. */
+@UsedByReflection("CastContext.java in cast_framework")
 public class CastOptionsProvider implements OptionsProvider {
     @Override
     public CastOptions getCastOptions(Context context) {