Introduce HostID and de-couple Extensions from "script injection System" [browser side]

chrome/common/extensions/manifest_handlers/content_scripts_handler.cc

Index: chrome/common/extensions/manifest_handlers/content_scripts_handler.cc
diff --git a/chrome/common/extensions/manifest_handlers/content_scripts_handler.cc b/chrome/common/extensions/manifest_handlers/content_scripts_handler.cc
index 7f7cba97a23f6ed9ec4d224d4045705af49098b8..6098eace3a6dfa2919413053a7021a05981b0035 100644
--- a/chrome/common/extensions/manifest_handlers/content_scripts_handler.cc
+++ b/chrome/common/extensions/manifest_handlers/content_scripts_handler.cc
@@ -16,6 +16,7 @@
 #include "extensions/common/error_utils.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extension_resource.h"
+#include "extensions/common/host_id.h"
 #include "extensions/common/manifest_constants.h"
 #include "extensions/common/manifest_handlers/permissions_parser.h"
 #include "extensions/common/permissions/permissions_data.h"
@@ -419,7 +420,7 @@ bool ContentScriptsHandler::Parse(Extension* extension, base::string16* error) {
       return false;  // Failed to parse script context definition.
     }
 
-    user_script.set_extension_id(extension->id());
+    user_script.set_host_id(HostID(HostID::EXTENSIONS, extension->id()));
     if (extension->converted_from_user_script()) {
       user_script.set_emulate_greasemonkey(true);
       // Greasemonkey matches all frames.