3671 [video_player] add http headers (cla: yes, p: video_player, platform-android, platform-ios)

3684 [shared_preferences] Fix concurrent modification of the shared preferences on Android (cla: yes, p: shared_preferences, platform-android)

3685 [image_picker] Implemented 2860 and added Unit Test to test functionality (cla: yes, p: image_picker, platform-android, waiting for tree to go green)

3694 [extension_google_sign_in_as_googleapis_auth] Deleted. (cla: yes, p: google_sign_in, platform-android, platform-ios, platform-web)