Created skeleton for switch access component extension.

chrome/common/extensions/extension_constants.h

Index: chrome/common/extensions/extension_constants.h
diff --git a/chrome/common/extensions/extension_constants.h b/chrome/common/extensions/extension_constants.h
index db333c8f60672163b64a5ceb201331cfe5eaf209..5f5d71434141370e43a41e916f26b8343f222e5c 100644
--- a/chrome/common/extensions/extension_constants.h
+++ b/chrome/common/extensions/extension_constants.h
@@ -203,6 +203,11 @@ extern const char kSelectToSpeakExtensionId[];
 // Path to preinstalled Select-to-speak extension (relative to
 // |chrome::DIR_RESOURCES|).
 extern const char kSelectToSpeakExtensionPath[];
+// The extension id of the Switch access extension.
+extern const char kSwitchAccessExtensionId[];
+// Path to preinstalled Switch access extension (relative to
+// |chrome::DIR_RESOURCES|).
+extern const char kSwitchAccessExtensionPath[];
 // Name of the manifest file in an extension when a special manifest is used
 // for guest mode.
 extern const char kGuestManifestFilename[];