Add font substitution metric for Linux

pdf/pdf_engine.h

 // Copyright (c) 2012 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_PDF_ENGINE_H_
 #define PDF_PDF_ENGINE_H_
 
 #include <stdint.h>
 
 #include "build/build_config.h"
@@ skipping 147 matching lines @@
 
     // Notifies the client that the engine has painted a page from the document.
     virtual void DocumentPaintOccurred() = 0;
 
     // Notifies the client that the document has finished loading.
     virtual void DocumentLoadComplete(int page_count) = 0;
 
     // Notifies the client that the document has failed to load.
     virtual void DocumentLoadFailed() = 0;
 
+    // Notifies the client that the document has requested substitute fonts.
+    virtual void FontSubstituted() = 0;
+
     virtual pp::Instance* GetPluginInstance() = 0;
 
     // Notifies that an unsupported feature in the PDF was encountered.
     virtual void DocumentHasUnsupportedFeature(const std::string& feature) = 0;
 
     // Notifies the client about document load progress.
     virtual void DocumentLoadProgress(uint32_t available,
                                       uint32_t doc_size) = 0;
 
     // Notifies the client about focus changes for form text fields.
@@ skipping 178 matching lines @@
 
   // See the definition of GetPDFPageSizeByIndex in pdf.cc for details.
   virtual bool GetPDFPageSizeByIndex(const void* pdf_buffer,
                                      int pdf_buffer_size, int page_number,
                                      double* width, double* height) = 0;
 };
 
 }  // namespace chrome_pdf
 
 #endif  // PDF_PDF_ENGINE_H_