Wrap MediaMetadata in base::Optional in content and chrome

chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java

Index: chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
index 0afeb246ac5826ea4d5f9bddda83956dbe4f58ab..77e02658e2445d14fc859e88d53c159211e62b56 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
@@ -104,11 +104,11 @@ public class MediaSessionTabHelper {
 
                 // The page's title is used as a placeholder if no title is specified in the
                 // metadata.
-                if (TextUtils.isEmpty(metadata.getTitle())) {
+                if (metadata == null || TextUtils.isEmpty(metadata.getTitle())) {
                     mFallbackMetadata = new MediaMetadata(
                             sanitizeMediaTitle(mTab.getTitle()),
-                            metadata.getArtist(),
-                            metadata.getAlbum());
+                            metadata == null ? "" : metadata.getArtist(),
+                            metadata == null ? "" : metadata.getAlbum());
                     metadata = mFallbackMetadata;
                 }