Add support for 'start_url' in Manifest.

content/public/common/manifest.h

Index: content/public/common/manifest.h
diff --git a/content/public/common/manifest.h b/content/public/common/manifest.h
index 4ee0957d434173ad2726af569df35bd671fae005..1b9b3c7ff4e77503723c5aa55c490d5f55e4b305 100644
--- a/content/public/common/manifest.h
+++ b/content/public/common/manifest.h
@@ -7,6 +7,7 @@
 
 #include "base/strings/nullable_string16.h"
 #include "content/common/content_export.h"
+#include "url/gurl.h"
 
 namespace content {
 
@@ -27,6 +28,9 @@ struct CONTENT_EXPORT Manifest {
   // Null if the parsing failed or the field was not present.
   base::NullableString16 short_name;
 
+  // Empty if the parsing failed or the field was not present.
+  GURL start_url;
+
   // Maximum length for all the strings inside the Manifest when it is sent over
   // IPC. The renderer process should truncate the strings before sending the
   // Manifest and the browser process must do the same when receiving it.