Add crash keys to LocalDOMWindow to help diagnose bug 621730.

chrome/common/crash_keys.cc

Index: chrome/common/crash_keys.cc
diff --git a/chrome/common/crash_keys.cc b/chrome/common/crash_keys.cc
index 65e96a42e4518b6c42b07d68b952efb224ccacd1..b66efe187f29ae16f038b03efa7571e5eb82bd0a 100644
--- a/chrome/common/crash_keys.cc
+++ b/chrome/common/crash_keys.cc
@@ -190,6 +190,11 @@ size_t RegisterChromeCrashKeys() {
     // Temporary for https://crbug.com/612711.
     { "aci_wrong_sp_extension_id", kSmallSize },
 
+    // Temporary for http://crbug.com/621730
+    { "postmessage_src_origin", kMediumSize },
+    { "postmessage_dst_origin", kMediumSize },
+    { "postmessage_dst_url", kLargeSize },
+
     // Temporary for https://crbug.com/616149.
     { "existing_extension_pref_value_type", crash_keys::kSmallSize },
   };