add activity indicator when configuring in reflow mode

For now pillow activityIndicator is used to draw animated waiting icon
at the upper left corner of the screen. So pillow service should be
enabled to use this feature, but eventually we should implement an
activity indicator that is independent of native system.

frontend/ui/readerui.lua

@@ -17,6 +17,7 @@ require "ui/reader/readerhinting"
 require "ui/reader/readerscreenshot"
 require "ui/reader/readerfrontlight"
 require "ui/reader/readerhyphenation"
+require "ui/reader/readeractivityindicator"
 
 --[[
 This is an abstraction for a reader interface
@@ -209,6 +210,14 @@ function ReaderUI:init()
 			document = self.document,
 		}
 		table.insert(self, coptlistener)
+		-- activity indicator
+		local activity_listener = ReaderActivityIndicator:new{
+			dialog = self.dialog,
+			view = self[1],
+			ui = self,
+			document = self.document,
+		}
+		table.insert(self, activity_listener)
 	end
 	--DEBUG(self.doc_settings)
 	-- we only read settings after all the widgets are initialized