Speculative fix when translating blob data to a file path

Accoding to the stack on crbug.com/410602, BlobData can be null.
However, I am not able to reproduce the bug with any test cases.
So this is just a safe speculative fix.

BUG=410602

Review URL: https://codereview.chromium.org/601043003

Cr-Commit-Position: refs/heads/master@{#297007}

content/browser/media/android/media_resource_getter_impl.cc

@@ -51,7 +51,13 @@ static void RequestPlatformPathFromBlobURL(
       ChromeBlobStorageContext::GetFor(browser_context);
   scoped_ptr<storage::BlobDataHandle> handle =
       context->context()->GetBlobDataFromPublicURL(url);
-  const std::vector<storage::BlobData::Item> items = handle->data()->items();
+  storage::BlobData* data = handle->data();
+  if (!data) {
+    ReturnResultOnUIThread(callback, "");
+    NOTREACHED();
+    return;
+  }
+  const std::vector<storage::BlobData::Item> items = data->items();
 
   // TODO(qinmin): handle the case when the blob data is not a single file.
   DLOG_IF(WARNING, items.size() != 1u)

media/base/android/media_player_bridge.cc

@@ -263,6 +263,11 @@ void MediaPlayerBridge::OnAuthCredentialsRetrieved(
 }
 
 void MediaPlayerBridge::ExtractMediaMetadata(const std::string& url) {
+  if (url.empty()) {
+    OnMediaError(MEDIA_ERROR_FORMAT);
+    return;
+  }
+
   int fd;
   int64 offset;
   int64 size;