Implement window.print() on Android

printing/printing_context.h

Index: printing/printing_context.h
diff --git a/printing/printing_context.h b/printing/printing_context.h
index 0cc4731a19e98169d44b25ad235810dcd0d34818..d9fda4a62bc5775ed5cbac339dd34d6f05f91e2c 100644
--- a/printing/printing_context.h
+++ b/printing/printing_context.h
@@ -38,11 +38,12 @@ class PRINTING_EXPORT PrintingContext {
     virtual std::string GetAppLocale() = 0;
   };
 
-  // Tri-state result for user behavior-dependent functions.
+  // Result for user behavior-dependent functions.
   enum Result {
     OK,
     CANCEL,
     FAILED,
+    SYSTEM_DIALOG_DONE,
   };
 
   virtual ~PrintingContext();
@@ -51,6 +52,10 @@ class PRINTING_EXPORT PrintingContext {
   // print settings are available.
   typedef base::Callback<void(Result)> PrintSettingsCallback;
 
+  // Called when a printing process initiated by a script finishes.
+  // It's required to synchronize window.print() calls on Android
+  virtual void RequestSystemDialog(const PrintSettingsCallback& cb);
+
   // Asks the user what printer and format should be used to print. Updates the
   // context with the select device settings. The result of the call is returned
   // in the callback. This is necessary for Linux, which only has an