Set crash key if WM_QUIT message is received on GPU message loop.

chrome/app/chrome_crash_reporter_client_win.cc

Index: chrome/app/chrome_crash_reporter_client_win.cc
diff --git a/chrome/app/chrome_crash_reporter_client_win.cc b/chrome/app/chrome_crash_reporter_client_win.cc
index 94f55772eaf1253b947cadbd7c6f2c3bb80bc54d..8e5a4063bad659033cf864ce69f4548ea753acf1 100644
--- a/chrome/app/chrome_crash_reporter_client_win.cc
+++ b/chrome/app/chrome_crash_reporter_client_win.cc
@@ -179,6 +179,9 @@ size_t RegisterCrashKeysHelper() {
       // Temporary for https://crbug.com/630496.
       {"swdh_get_registration_cannot_host_url", crash_keys::kLargeSize},
       {"swdh_get_registration_cannot_document_url", crash_keys::kLargeSize},
+
+      // Temporary for https://crbug.com/647068.
+      {"received_quit_message", crash_keys::kSmallSize},
   };
 
   // This dynamic set of keys is used for sets of key value pairs when gathering