Differential updates for components.

extensions/common/crx_file.h

Index: extensions/common/crx_file.h
diff --git a/extensions/common/crx_file.h b/extensions/common/crx_file.h
index cb450afb434c9258962717181075139198f7ea25..3ac81897925fc1365ab65f78842e65cf3e63473b 100644
--- a/extensions/common/crx_file.h
+++ b/extensions/common/crx_file.h
@@ -60,6 +60,10 @@ class CrxFile {
   // Returns the header structure for writing out to a CRX file.
   const Header& header() const { return header_; }
 
+  // Checks a valid |header| to determine whether or not the CRX represents a
+  // differential CRX.
+  static bool HeaderIsDelta(const Header& header);
+
  private:
   Header header_;