Suppress the exception thrown when responding to message with no response callback.

chrome/browser/resources/hotword_helper/manager.js

Index: chrome/browser/resources/hotword_helper/manager.js
diff --git a/chrome/browser/resources/hotword_helper/manager.js b/chrome/browser/resources/hotword_helper/manager.js
index 4ce86db62959d7fb42ade923a8d80fb11daa24f2..7e325ab07e50101b6a9444a7f499364fb173fc06 100644
--- a/chrome/browser/resources/hotword_helper/manager.js
+++ b/chrome/browser/resources/hotword_helper/manager.js
@@ -58,19 +58,28 @@ OptInManager.CommandFromPage = {
  */
 OptInManager.prototype.injectTab_ = function(
     tab, sendResponse, hotwordStatus) {
-  if (tab.incognito || !hotwordStatus.available) {
-    sendResponse({'doNotShowOptinMessage': true});
-    return;
-  }
+  try {
+    if (tab.incognito || !hotwordStatus.available) {
+      sendResponse({'doNotShowOptinMessage': true});
+      return;
+    }
 
-  if (!hotwordStatus.enabledSet) {
-    sendResponse(hotwordStatus);
-    return;
-  }
+    if (!hotwordStatus.enabledSet) {
+      sendResponse(hotwordStatus);
+      return;
+    }
 
-  if (hotwordStatus.enabled)
-    chrome.tabs.executeScript(tab.id, {'file': 'audio_client.js'});
-  sendResponse({'doNotShowOptinMessage': true});
+    if (hotwordStatus.enabled)
+      chrome.tabs.executeScript(tab.id, {'file': 'audio_client.js'});
+    sendResponse({'doNotShowOptinMessage': true});
+  } catch (err) {
+    // Suppress the exception thrown when the page doesn't specify a response
+    // callback. Unfortunately, there doesn't appear to be a way to detect
+    // one-way messages without explicitly saying in the message itself.
+    if (err.message == 'Attempting to use a disconnected port object')

[rpetterson, 2014/09/22 23:04:41]

Weird question, but is this always going to be in english or the same phrasing?
It would seem that an error code would be better if possible.

[Anand Mistry (off Chromium), 2014/09/22 23:50:43]

It's an untranslated constant in
https://code.google.com/p/chromium/codesearch#chromium/src/extensions/rendere...

I realise this is brittle, but I'm afraid to change this exception to be
something other than a string since it might break existing apps which have
discovered this (undocumented) behaviour.

[rpetterson, 2014/09/22 23:53:03]

Understood. Please add a note to the comment listing where this string is
defined.

[Anand Mistry (off Chromium), 2014/09/23 00:31:30]

Done.

+      return;
+    throw err;
+  }
 };