Add skia extension to allow setting default fontmgr on linux. Use it to allow the linux blimp clien…

blimp/client/core/switches/blimp_client_switches.h

Index: blimp/client/core/switches/blimp_client_switches.h
diff --git a/blimp/client/core/switches/blimp_client_switches.h b/blimp/client/core/switches/blimp_client_switches.h
index 4a0658f16307d610bf48b5cf5d3320c8a59846e7..d376a9684da1db59b41a1238d3d87163aec662fb 100644
--- a/blimp/client/core/switches/blimp_client_switches.h
+++ b/blimp/client/core/switches/blimp_client_switches.h
@@ -36,6 +36,9 @@ extern const char kEngineTransport[];
 // Enables downloading the complete page from the engine.
 extern const char kDownloadWholeDocument[];
 
+// Specifies directory where android fonts are stored for use in Linux client.
+extern const char kAndroidFontsPath[];
+
 }  // namespace switches
 }  // namespace blimp