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..9aecee1dca8eee0f7d9484a7c35f028c4a71cbd6 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 {
+    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});

[Dan Beam, 2014/09/23 03:35:38]

^ which of these lines actually throw?

[Anand Mistry (off Chromium), 2014/09/23 03:55:07]

In theory, any of these calls to sendResponse() could throw (hence the large try
block), but it's the last one that I've seen in practice.

+  } 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.
+    // 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 03:35:38]

does sendResponse() need to be invoked here?

[Anand Mistry (off Chromium), 2014/09/23 03:55:07]

No. It's the sendResponse() that threw the exception. I've clarified the comment
to say that sendResponse throws.

+      return;
+    throw err;
+  }
 };