Adding support to retrieve remaining and total space on disk/file shelf.

chrome/browser/extensions/extension_file_browser_private_api.h

Index: chrome/browser/extensions/extension_file_browser_private_api.h
diff --git a/chrome/browser/extensions/extension_file_browser_private_api.h b/chrome/browser/extensions/extension_file_browser_private_api.h
index 7c7716dfe228003d9691b9a592efbad1cfe152a9..a1622fb1b9b8cf0f91650d379c44a03033830bd8 100644
--- a/chrome/browser/extensions/extension_file_browser_private_api.h
+++ b/chrome/browser/extensions/extension_file_browser_private_api.h
@@ -296,6 +296,35 @@ class FormatDeviceFunction
   DECLARE_EXTENSION_FUNCTION_NAME("fileBrowserPrivate.formatDevice");
 };
 
+class GetSizeStatsFunction
+    :
+#ifdef OS_CHROMEOS
+      public chromeos::MountLibrary::CallbackDelegate,
+#endif
+      public FileBrowserFunction {
+ public:
+  GetSizeStatsFunction();
+
+#ifdef OS_CHROMEOS
+  // chromeos::MountLibrary::CallbackDelegate implementation.
+  void GetSizeStatsCallback(const char* mount_path,
+                            bool success,
+                            size_t total_size_kb,
+                            size_t remaining_size_kb) OVERRIDE;
+#endif
+
+ protected:
+  virtual ~GetSizeStatsFunction();
+
+  // FileBrowserFunction overrides.
+  virtual bool RunImpl() OVERRIDE;
+  virtual void GetLocalPathsResponseOnUIThread(const FilePathList& files,
+                                               void* context) OVERRIDE;
+
+ private:
+  DECLARE_EXTENSION_FUNCTION_NAME("fileBrowserPrivate.getSizeStats");
+};
+
 // Retrieves devices meta-data. Expects volume's device path as an argument.
 class GetVolumeMetadataFunction
     : public SyncExtensionFunction {