linux_aura: Implement file drag and drop in content area.

ui/base/dragdrop/os_exchange_data_provider_aurax11.h

Index: ui/base/dragdrop/os_exchange_data_provider_aurax11.h
diff --git a/ui/base/dragdrop/os_exchange_data_provider_aurax11.h b/ui/base/dragdrop/os_exchange_data_provider_aurax11.h
index 0d16351e5b8f5198ba722d567033c47cb3d55c7d..c83f955ab8a08a4a1ea986cd2cd6ded2722d5cb6 100644
--- a/ui/base/dragdrop/os_exchange_data_provider_aurax11.h
+++ b/ui/base/dragdrop/os_exchange_data_provider_aurax11.h
@@ -27,6 +27,7 @@
 namespace ui {
 
 class Clipboard;
+class OSExchangeDataProviderAuraX11Test;
 
 // OSExchangeData::Provider implementation for aura on linux.
 class UI_BASE_EXPORT OSExchangeDataProviderAuraX11
@@ -90,6 +91,7 @@ class UI_BASE_EXPORT OSExchangeDataProviderAuraX11
   virtual bool Dispatch(const base::NativeEvent& event) OVERRIDE;
 
  private:
+  friend class OSExchangeDataProviderAuraX11Test;
   typedef std::map<OSExchangeData::CustomFormat, Pickle>  PickleData;
 
   // Returns true if |formats_| contains a string format and the string can be