Make 'License' field in third-party metadata required

This will simplify the addition of a tool to check licenses for the purpose of
the Android WebView build.

See also http://codereview.chromium.org/10827099

Also adds other missing fields to these README.chromium files as required by
presubmit checks and fixes a regex used to enforce this.

BUG=138921

Review URL: https://chromiumcodereview.appspot.com/10821103

git-svn-id: http://src.chromium.org/svn/trunk/src/third_party/gles2_book@149423 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
diff --git a/README.chromium b/README.chromium
index 393c2c5..753e407 100644
--- a/README.chromium
+++ b/README.chromium
@@ -3,6 +3,7 @@
 URL: http://opengles-book.com/
 Version: unknown
 Security Critical: no
+License: MIT
 
 Description:
 Code samples from OpenGL ES 2.0 Programming Guide.
@@ -10,6 +11,8 @@
 Publisher: Addison-Wesley Professional
 ISBN: 0321502795
 
+Sample code is MIT licensed - http://www.opengles-book.com/downloads.html
+
 Local Modifications:
   Removed files that chromium did not need:
     - Bin/*