Add Blimp feedback data about visible BlimpContents.

blimp/client/core/feedback/blimp_feedback_data.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BLIMP_CLIENT_CORE_FEEDBACK_BLIMP_FEEDBACK_DATA_H_
 #define BLIMP_CLIENT_CORE_FEEDBACK_BLIMP_FEEDBACK_DATA_H_
 
 #include <string>
 #include <unordered_map>
 
 namespace blimp {
 namespace client {
+class BlimpContentsManager;
+
 // Denotes whether Blimp is supported in the current.
 extern const char kFeedbackSupportedKey[];
+// Denotes whether there exists any visible BlimpContents.
+extern const char kFeedbackHasVisibleBlimpContents[];
 
 // Creates a data object containing data about Blimp to be used for feedback.
-std::unordered_map<std::string, std::string> CreateBlimpFeedbackData();
+std::unordered_map<std::string, std::string> CreateBlimpFeedbackData(
+    BlimpContentsManager* blimp_contents_manager);
 
 }  // namespace client
 }  // namespace blimp
 
 #endif  // BLIMP_CLIENT_CORE_FEEDBACK_BLIMP_FEEDBACK_DATA_H_