Revert of Remove font cache code

content/public/common/dwrite_font_platform_win.h

+// Copyright 2014 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 CONTENT_PUBLIC_COMMON_DWRITE_FONT_PLATFORM_WIN_H_
+#define CONTENT_PUBLIC_COMMON_DWRITE_FONT_PLATFORM_WIN_H_
+
+#include "base/files/file.h"
+#include "content/common/content_export.h"
+
+struct IDWriteFactory;
+struct IDWriteFontCollection;
+
+namespace content {
+
+// This is the shared section that is used between browser and renderer for
+// loading font cache. Section name is suffixed with browser process id so that
+// multiple instance chrome scenario works fine.
+CONTENT_EXPORT extern const char kFontCacheSharedSectionName[];
+
+// Function returns custom font collection in terms of IDWriteFontCollection.
+// This function maintains singleton instance of font collection and returns
+// it on repeated calls.
+CONTENT_EXPORT IDWriteFontCollection* GetCustomFontCollection(
+    IDWriteFactory* factory);
+
+// Builds static font cache. As this function need to iterate through all
+// available fonts in the system, it may take a while.
+CONTENT_EXPORT bool BuildFontCache(const base::FilePath& file);
+
+// Loads font cache from file. This is supposed to be used from browser
+// side where loading means creating readonly shared memory file mapping so that
+// renderers can read from it.
+CONTENT_EXPORT bool LoadFontCache(const base::FilePath& path);
+
+// Added in header mainly for unittest
+CONTENT_EXPORT bool ValidateFontCacheFile(base::File* file);
+
+// Determines whether code should use the DirectWrite font proxy codepath.
+// Note that this function only checks whether the field trial is enabled.
+// Callers are still expected to take appropriate action based on the return
+// value.
+CONTENT_EXPORT bool ShouldUseDirectWriteFontProxyFieldTrial();
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_COMMON_DWRITE_FONT_PLATFORM_WIN_H_