Add unit tests for RedirectToFileResourceHandler.

content/browser/loader/redirect_to_file_resource_handler.h

Index: content/browser/loader/redirect_to_file_resource_handler.h
diff --git a/content/browser/loader/redirect_to_file_resource_handler.h b/content/browser/loader/redirect_to_file_resource_handler.h
index 8163a4246feb88de98192ff304b151f4746d0064..bdd59e077304eaa587f9bf3c7dc99c23fdf09b12 100644
--- a/content/browser/loader/redirect_to_file_resource_handler.h
+++ b/content/browser/loader/redirect_to_file_resource_handler.h
@@ -40,6 +40,10 @@ namespace content {
 class CONTENT_EXPORT RedirectToFileResourceHandler
     : public LayeredResourceHandler {
  public:
+  // Exposed for testing.
+  static const int kInitialReadBufSize;
+  static const int kMaxReadBufSize;
+
   typedef base::Callback<void(const CreateTemporaryFileStreamCallback&)>
       CreateTemporaryFileStreamFunction;
 
@@ -66,6 +70,9 @@ class CONTENT_EXPORT RedirectToFileResourceHandler
   void OnResponseCompleted(const net::URLRequestStatus& status,
                            bool* defer) override;
 
+  // Returns the size of |buf_|, to make sure it's being increased as expected.
+  int GetBufferSizeForTesting() const;
+
  private:
   void DidCreateTemporaryFile(base::File::Error error_code,
                               std::unique_ptr<net::FileStream> file_stream,