Introduce runtime.onSuspendCanceled() event.

chrome/common/extensions/api/runtime.json

Index: chrome/common/extensions/api/runtime.json
diff --git a/chrome/common/extensions/api/runtime.json b/chrome/common/extensions/api/runtime.json
index 8c9b1dd6ef7e4fa1a89cc354b708e08635bb26fc..822eb5c5d7dbc01e66be9905336ebcde73a99d9c 100644
--- a/chrome/common/extensions/api/runtime.json
+++ b/chrome/common/extensions/api/runtime.json
@@ -117,7 +117,12 @@
       {
         "name": "onSuspend",
         "type": "function",
-        "description": "Sent to the event page just before it is unloaded. This gives the extension opportunity to do some clean up. Note that since the page is unloading, any asynchronous operations started while handling this event are not guaranteed to complete."
+        "description": "Sent to the event page just before it is unloaded. This gives the extension opportunity to do some clean up. Note that since the page is unloading, any asynchronous operations started while handling this event are not guaranteed to complete. If more activity for the event page occurs before it gets unloaded the onSuspendCanceled event will be sent and the page won't be unloaded. "
+      },
+      {
+        "name": "onSuspendCanceled",
+        "type": "function",
+        "description": "Sent after onSuspend() to indicate that the app won't be unloaded after all."
       }
     ]
   }