Linux: Add support for chrooted renderers.

skia/ext/SkFontHost_fontconfig_impl.h

+/* libs/graphics/ports/SkFontHost_fontconfig_impl.h
+**
+** Copyright 2009, Google Inc.
+**
+** Licensed under the Apache License, Version 2.0 (the "License");
+** you may not use this file except in compliance with the License.
+** You may obtain a copy of the License at
+**
+**     http://www.apache.org/licenses/LICENSE-2.0
+**
+** Unless required by applicable law or agreed to in writing, software
+** distributed under the License is distributed on an "AS IS" BASIS,
+** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+** See the License for the specific language governing permissions and
+** limitations under the License.
+*/
+
+/* The SkFontHost_fontconfig code requires an implementation of an abstact
+ * fontconfig interface. We do this because sometimes fontconfig is not
+ * directly availible and this provides an ability to change the fontconfig
+ * implementation at run-time.
+ */
+
+#ifndef FontConfigInterface_DEFINED
+#define FontConfigInterface_DEFINED
+
+#include <string>
+
+class FontConfigInterface {
+  public:
+    virtual ~FontConfigInterface() { }
+
+    /** Performs config match
+     *
+     *  @param result_family (output) on success, the resulting family name.
+     *  @param result_fileid (output) on success, the resulting file id.
+     *  @param fileid_valid if true, then |fileid| is valid
+     *  @param fileid the fileid (as returned by this function) which we are
+     *    trying to match.
+     *  @param family (optional) the family of the font that we are trying to
+     *    match.
+     *  @param is_bold (optional, set to -1 to ignore)
+     *  @param is_italic (optional, set to -1 to ignore)
+     *  @return true iff successful.
+     */
+    virtual bool Match(
+          std::string* result_family,
+          unsigned* result_fileid,
+          bool fileid_valid,
+          unsigned fileid,
+          const std::string& family,
+          int is_bold,
+          int is_italic) = 0;
+
+    /** Open a font file given the fileid as returned by Match
+     */
+    virtual int Open(unsigned fileid) = 0;
+};
+
+#endif  // FontConfigInterface_DEFINED