Do not typedef ExtensionId/ID, since it's already available in extension_id.h

chrome/browser/extensions/api/image_writer_private/operation.h

Index: chrome/browser/extensions/api/image_writer_private/operation.h
diff --git a/chrome/browser/extensions/api/image_writer_private/operation.h b/chrome/browser/extensions/api/image_writer_private/operation.h
index 6710298ca94f7ed83f3dc8c408e82246d9044f02..98412b700a779514cdf072f5a739be1f73d259bc 100644
--- a/chrome/browser/extensions/api/image_writer_private/operation.h
+++ b/chrome/browser/extensions/api/image_writer_private/operation.h
@@ -19,7 +19,7 @@
 #include "build/build_config.h"
 #include "chrome/browser/extensions/api/image_writer_private/image_writer_utility_client.h"
 #include "chrome/common/extensions/api/image_writer_private.h"
-
+#include "extensions/common/extension_id.h"
 
 namespace image_writer_api = extensions::api::image_writer_private;
 
@@ -59,7 +59,6 @@ class Operation : public base::RefCountedThreadSafe<Operation> {
  public:
   typedef base::Callback<void(bool, const std::string&)> StartWriteCallback;
   typedef base::Callback<void(bool, const std::string&)> CancelWriteCallback;
-  typedef std::string ExtensionId;
 
   Operation(base::WeakPtr<OperationManager> manager,
             const ExtensionId& extension_id,