Add isWritableFileEntry to the fileSystem API

chrome/browser/extensions/api/file_system/file_system_api.h

Index: chrome/browser/extensions/api/file_system/file_system_api.h
diff --git a/chrome/browser/extensions/api/file_system/file_system_api.h b/chrome/browser/extensions/api/file_system/file_system_api.h
index b3a58d2b92dd99f9dd943005094254fd37de90da..f65649ed53df65d00c02822f1aafd80bf5c83d32 100644
--- a/chrome/browser/extensions/api/file_system/file_system_api.h
+++ b/chrome/browser/extensions/api/file_system/file_system_api.h
@@ -54,6 +54,15 @@ class FileSystemGetWritableFileEntryFunction : public FileSystemEntryFunction {
   virtual bool RunImpl() OVERRIDE;
 };
 
+class FileSystemIsWritableFileEntryFunction : public SyncExtensionFunction {
+ public:
+  DECLARE_EXTENSION_FUNCTION_NAME("fileSystem.isWritableFileEntry");
+
+ protected:
+  virtual ~FileSystemIsWritableFileEntryFunction() {}
+  virtual bool RunImpl() OVERRIDE;
+};
+
 class FileSystemChooseFileFunction : public FileSystemEntryFunction {
  public:
   // Allow picker UI to be skipped in testing.