Make the PDF viewer background color a property of the instance.

pdf/preview_mode_client.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PDF_PREVIEW_MODE_CLIENT_H_
 #define PDF_PREVIEW_MODE_CLIENT_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 49 matching lines @@
                             bool case_sensitive,
                             std::vector<SearchStringResult>* results);
   virtual void DocumentPaintOccurred();
   virtual void DocumentLoadComplete(int page_count);
   virtual void DocumentLoadFailed();
   virtual pp::Instance* GetPluginInstance();
   virtual void DocumentHasUnsupportedFeature(const std::string& feature);
   virtual void DocumentLoadProgress(uint32 available, uint32 doc_size);
   virtual void FormTextFieldFocusChange(bool in_focus);
   virtual bool IsPrintPreview();
+  virtual uint32 GetBackgroundColor();
 
  private:
   Client* client_;
 };
 
 }  // namespace chrome_pdf
 
 #endif  // PDF_PREVIEW_MODE_CLIENT_H_