Fix bug in shut down of HTMLViewer

components/font_service/public/cpp/font_loader.h

 // Copyright 2015 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 COMPONENTS_FONT_SERVICE_PUBLIC_CPP_FONT_LOADER_H_
 #define COMPONENTS_FONT_SERVICE_PUBLIC_CPP_FONT_LOADER_H_
 
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
@@ skipping 19 matching lines @@
 // also see the FontServiceThread class.)
 //
 // This is the mojo equivalent to content/common/font_config_ipc_linux.h
 class FontLoader : public SkFontConfigInterface,
                    public internal::MappedFontFile::Observer {
  public:
   explicit FontLoader(mojo::Shell* shell);
   explicit FontLoader(mojo::ApplicationImpl* application_impl);
   ~FontLoader() override;
 
+  // Shuts down the background thread.
+  void Shutdown();
+
   // SkFontConfigInterface:
   bool matchFamilyName(const char family_name[],
                        SkTypeface::Style requested,
                        FontIdentity* out_font_identifier,
                        SkString* out_family_name,
                        SkTypeface::Style* out_style) override;
   SkStreamAsset* openStream(const FontIdentity& identity) override;
 
  private:
   // internal::MappedFontFile::Observer:
@@ skipping 10 matching lines @@
 
   // Maps font identity ID to the memory-mapped file with font data.
   base::hash_map<uint32_t, internal::MappedFontFile*> mapped_font_files_;
 
   DISALLOW_COPY_AND_ASSIGN(FontLoader);
 };
 
 }  // namespace font_service
 
 #endif  // COMPONENTS_FONT_SERVICE_PUBLIC_CPP_FONT_LOADER_H_