Rolled ANGLE to r531.

This will pull in a fix for the bugs below.

TEST=try
BUG=69470,69573

Review URL: http://codereview.chromium.org/6248005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71389 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -34,7 +34,7 @@ deps = {
     (Var("googlecode_url") % "googletest") + "/trunk@492",
 
   "src/third_party/angle":
-    (Var("googlecode_url") % "angleproject") + "/trunk@530",
+    (Var("googlecode_url") % "angleproject") + "/trunk@531",
 
   "src/third_party/WebKit":
     "/trunk/deps/third_party/WebKit@71060",