Bug 1166351 - Add instrumentation to try to figure out why tabbrowser-remote-browser binding is sometimes removed. r=felipe.

--HG--
extra : commitid : 1s4eJ2vMO1W
extra : rebase_source : 891fb1234554dac25b9aeadb16e749e284dfaf80
extra : amend_source : e0ce278be8277fcd892c5aea300a58df2cfd65de

browser/base/content/tabbrowser.xml

@@ -3371,6 +3371,16 @@
                 return;
               }
 
+              // Instrumentation to figure out bug 1166351 - if the binding
+              // on the browser we're switching to has gone away, try to find out
+              // why. We should remove this and the checkBrowserBindingAlive
+              // method once bug 1166351 has been closed.
+              if (this.tabbrowser.AppConstants.E10S_TESTING_ONLY &&
+                  !this.checkBrowserBindingAlive(tab)) {
+                Cu.reportError("Please report the above errors in bug 1166351.");
+                return;
+              }
+
               this.logState("requestTab " + this.tinfo(tab));
               this.startTabSwitch();
 
@@ -3466,6 +3476,40 @@
               return this._shouldLog;
             },
 
+            // Instrumentation for bug 1166351
+            checkBrowserBindingAlive: function(tab) {
+              let err = Cu.reportError;
+
+              if (!tab.linkedBrowser) {
+                err("Attempting to switch to tab that has no linkedBrowser.");
+                return false;
+              }
+
+              let b = tab.linkedBrowser;
+
+              if (!b.isRemoteBrowser) {
+                // non-remote browsers are not the problem.
+                return true;
+              }
+
+              if (!b._alive) {
+                // The browser binding has been removed. Dump a bunch of
+                // diagnostic information to the browser console.
+                err("The tabbrowser-remote-browser binding has been removed " +
+                    "from the tab being switched to.");
+                err("MozBinding is currently: " +
+                    window.getComputedStyle(b).MozBinding);
+                if (!b.parentNode) {
+                  err("Browser was removed from the DOM.");
+                } else {
+                  err("Parent is: " + b.parentNode.outerHTML);
+                }
+                return false;
+              }
+
+              return true;
+            },
+
             tinfo: function(tab) {
               if (tab) {
                 return tab._tPos + "(" + tab.linkedBrowser.currentURI.spec + ")";
@@ -6117,6 +6161,8 @@
   <binding id="tabbrowser-remote-browser"
            extends="chrome://global/content/bindings/remote-browser.xml#remote-browser">
     <implementation>
+      <!-- This will go away if the binding has been removed for some reason. -->
+      <field name="_alive">true</field>
       <!-- throws exception for unknown schemes -->
       <method name="loadURIWithFlags">
         <parameter name="aURI"/>