Add early-injection capability to user scripts. I haven't yet

chrome/browser/extensions/extension.h

Index: chrome/browser/extensions/extension.h
diff --git a/chrome/browser/extensions/extension.h b/chrome/browser/extensions/extension.h
index 22e8fd61f8dd1a6071053a07e46064273f112b0a..5964ad4f10e4257a05edd9319feeed733812c9ec 100644
--- a/chrome/browser/extensions/extension.h
+++ b/chrome/browser/extensions/extension.h
@@ -44,9 +44,14 @@ class Extension {
   static const wchar_t* kMatchesKey;
   static const wchar_t* kNameKey;
   static const wchar_t* kUserScriptsKey;
+  static const wchar_t* kRunAtKey;
   static const wchar_t* kVersionKey;
   static const wchar_t* kZipHashKey;
 
+  // Some values expected in manifests.
+  static const char* kRunAtDocumentStartValue;
+  static const char* kRunAtDocumentEndValue;
+
   // Error messages returned from InitFromValue().
   static const char* kInvalidDescriptionError;
   static const char* kInvalidFileCountError;
@@ -59,6 +64,7 @@ class Extension {
   static const char* kInvalidMatchError;
   static const char* kInvalidMatchesError;
   static const char* kInvalidNameError;
+  static const char* kInvalidRunAtError;
   static const char* kInvalidUserScriptError;
   static const char* kInvalidUserScriptsListError;
   static const char* kInvalidVersionError;