Require unpacked extensions to use mainfest_version 2.

BUG=62897
Review URL: http://codereview.chromium.org/8773032

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113564 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/extension.cc

@@ -57,7 +57,7 @@ using extensions::csp_validator::ContentSecurityPolicyIsSecure;
 
 namespace {
 
-const int kModernManifestVersion = 1;
+const int kModernManifestVersion = 2;
 const int kPEMOutputColumns = 65;
 
 // KEY MARKERS