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..03739fa64d68950ce5b6f5eea424db448a67d68b 100644
--- a/chrome/browser/resources/hotword_helper/manager.js
+++ b/chrome/browser/resources/hotword_helper/manager.js
@@ -58,19 +58,30 @@ OptInManager.CommandFromPage = {
  */
 OptInManager.prototype.injectTab_ = function(
     tab, sendResponse, hotwordStatus) {
-  if (tab.incognito || !hotwordStatus.available) {
-    sendResponse({'doNotShowOptinMessage': true});
-    return;
-  }
+  try {

[Dan Beam, 2014/09/23 04:14:00]

nit: if sendReponse() is what throws, i'd think it's best to do try/catch only
around that call, e.g.

  var response = ...;
  if (...)
    response = ...;
  else if (...)
    response = ...;

  try {
    sendResponse(response);
  } catch(e) {
    ...
  }

[Anand Mistry (off Chromium), 2014/09/24 01:11:40]

Done.

+    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'});

[Dan Beam, 2014/09/23 04:14:00]

nit: \n

[Anand Mistry (off Chromium), 2014/09/24 01:11:41]

Done.

+    sendResponse({'doNotShowOptinMessage': true});
+  } catch (err) {
+    // Suppress the exception thrown by sendResponse() when the page doesn't
+    // specify a response callback in the call to chrome.runtime.sendMessage().
+    // Unfortunately, there doesn't appear to be a way to detect one-way
+    // messages without explicitly saying in the message itself.  This message
+    // is defined as a constant in extensions/renderer/messaging_bindings.cc
+    if (err.message == 'Attempting to use a disconnected port object')

[Dan Beam, 2014/09/23 04:14:00]

can you write a test that exercises this case? (so there's a shred of hope of it
breaking if the error message changes)

[Anand Mistry (off Chromium), 2014/09/24 01:11:41]

I've given it a shot.

+      return;
+    throw err;
+  }
 };