Adds a webstorePrivate method for silently installing extensions.

chrome/browser/extensions/extension_browsertest.h

Index: chrome/browser/extensions/extension_browsertest.h
diff --git a/chrome/browser/extensions/extension_browsertest.h b/chrome/browser/extensions/extension_browsertest.h
index 30645ed5ed4315a2e37bdf33d726a49205830a39..10e0d8ae156dfbcac4ac4730686990bbfa37192b 100644
--- a/chrome/browser/extensions/extension_browsertest.h
+++ b/chrome/browser/extensions/extension_browsertest.h
@@ -43,6 +43,15 @@ class ExtensionBrowserTest
   // Return an empty FilePath if there were errors.
   FilePath PackExtension(const FilePath& dir_path);
 
+  // Pack the extension in |dir_path| into a crx file at |crx_path|, using the
+  // key |pem_path|. If |pem_path| does not exist, create a new key at
+  // |pem_out_path|.
+  // Return the path to the crx file, or an empty FilePath if there were errors.
+  FilePath PackExtensionWithOptions(const FilePath& dir_path,
+                                    const FilePath& crx_path,
+                                    const FilePath& pem_path,
+                                    const FilePath& pem_out_path);
+
   // |expected_change| indicates how many extensions should be installed (or
   // disabled, if negative).
   // 1 means you expect a new install, 0 means you expect an upgrade, -1 means