Fix history page middle click action

chrome/browser/resources/synthetic_middleclick.js

Index: chrome/browser/resources/synthetic_middleclick.js
diff --git a/chrome/browser/resources/ntp4/synthetic_middleclick.js b/chrome/browser/resources/synthetic_middleclick.js
similarity index 70%
rename from chrome/browser/resources/ntp4/synthetic_middleclick.js
rename to chrome/browser/resources/synthetic_middleclick.js
index 8c90c98a7f5abab97c059ede25c5e2a1345170b4..2045d3facf5c659f45e72efaad4768adfb51e65c 100644
--- a/chrome/browser/resources/ntp4/synthetic_middleclick.js
+++ b/chrome/browser/resources/synthetic_middleclick.js
@@ -21,4 +21,12 @@ document.addEventListener('mouseup', function(e) {
   middleButtonMouseDownTarget = null;
 }, true);
 
+// Prevent the synthetic click to open a new tab as the new tab will
+// open if the click happened on a link regardless of this synthetic
+// event.

[Dan Beam, 2016/05/31 21:34:32]

i don't understand what this comment means.  can you try again?

[Navid Zolghadr, 2016/06/01 18:46:16]

How about this?

+window.addEventListener('click', function(e) {
+  if (e.button == 1 && !e.isTrusted)

[Dan Beam, 2016/05/31 21:34:32]

don't we control the code that's doing this?  why not just do:

if (e.path.length > 0 && e.path[0] == middleButtonMouseDownTarget) {
  var click = new MouseEvent('click', e);
  middleButtonMouseDownTarget.dispatchEvent(click);
  click.preventDefault();
}

[Navid Zolghadr, 2016/06/01 18:46:16]

Maybe the new comment explains this a little better. Basically when js
dispatches the click event the default handlers will run right after all the
handlers. So basically your proposal doesn't prevent the default behavior of the
click event as the new tab is already opened right before the
click.preventDefault() line. So I need to preventDefault it in a handler (that
runs the last preferably). The other solution is to prevent defaulting it before
dispatching it but that causes some unexpected behavior in the current code as
the handlers we have here ignores the events if they were preventDefaulted
already.

+    e.preventDefault();
+});
+
 })();