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 225174cb82efdbe1c4b107b1c3b25f09b0a9a5d0..bf26b1a9fc5791c114735b717da675406ea5cf2b 100644
--- a/chrome/common/crash_keys.cc
+++ b/chrome/common/crash_keys.cc
@@ -194,6 +194,11 @@ 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 },
   };