Implement the onBeforeRetarget event of the webNavigation API

chrome/test/data/extensions/api_test/webnavigation/navigation2/test.html

 <script>
 var expectedEventData;
 var capturedEventData;
 var nextFrameId;
 var frameIds;
+var nextTabId;
+var tabIds;
 
 function expect(data) {
   expectedEventData = data;
   capturedEventData = [];
   nextFrameId = 1;
   frameIds = {};
+  nextTabId = 0;
+  tabIds = {};
 }
 
 function checkExpectations() {
   if (capturedEventData.length < expectedEventData.length) {
     return;
   }
   chrome.test.assertEq(JSON.stringify(expectedEventData),
       JSON.stringify(capturedEventData));
   chrome.test.succeed();
 }
 
 function captureEvent(name, details) {
   // normalize details.
-  details.timeStamp = 0;
-  if (details.frameId != 0) {
+  if ('timeStamp' in details) {
+    details.timeStamp = 0;
+  }
+  if (('frameId' in details) && (details.frameId != 0)) {
     if (frameIds[details.frameId] === undefined) {
       frameIds[details.frameId] = nextFrameId++;
     }
     details.frameId = frameIds[details.frameId];
   }
+  if ('tabId' in details) {
+    if (tabIds[details.tabId] === undefined) {
+      tabIds[details.tabId] = nextTabId++;
+    }
+    details.tabId = tabIds[details.tabId];
+  }
+  if ('sourceTabId' in details) {
+    if (tabIds[details.sourceTabId] === undefined) {
+      tabIds[details.sourceTabId] = nextTabId++;
+    }
+    details.sourceTabId = tabIds[details.sourceTabId];
+  }
   capturedEventData.push([name, details]);
   checkExpectations();
 }
 
 chrome.experimental.webNavigation.onBeforeNavigate.addListener(
   function(details) {
     captureEvent("onBeforeNavigate", details);
 });
 
 chrome.experimental.webNavigation.onCommitted.addListener(function(details) {
   captureEvent("onCommitted", details);
 });
 
 chrome.experimental.webNavigation.onDOMContentLoaded.addListener(
   function(details) {
     captureEvent("onDOMContentLoaded", details);
 });
 
 chrome.experimental.webNavigation.onCompleted.addListener(
   function(details) {
     captureEvent("onCompleted", details);
 });
 
+chrome.experimental.webNavigation.onBeforeRetarget.addListener(
+  function(details) {
+    captureEvent("onBeforeRetarget", details);
+});
+
 chrome.experimental.webNavigation.onErrorOccurred.addListener(
   function(details) {
     captureEvent("onErrorOccurred", details);
 });
 
 var getURL = chrome.extension.getURL;
 chrome.tabs.getSelected(null, function(tab) {
   var tabId = tab.id;
 
   chrome.test.runTests([
     /* Navigates to a non-existant page. */
     function nonExistant() {
       expect([
         [ "onBeforeNavigate",
           { frameId: 0,
             requestId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('nonexistant.html') }],
         [ "onErrorOccurred",
           { error: "net::ERR_FILE_NOT_FOUND",
             frameId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('nonexistant.html') }]]);
       chrome.tabs.update(tabId, { url: getURL('nonexistant.html') });
     },
 
     /* An page that tries to load an non-existant iframe. */
     function nonExistantIframe() {
       expect([
         [ "onBeforeNavigate",
           { frameId: 0,
             requestId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/d.html') }],
         [ "onCommitted",
           { frameId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             transitionQualifiers: "",
             transitionType: "link",
             url: getURL('iframeFail/d.html') }],
         [ "onBeforeNavigate",
           { frameId: 1,
             requestId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/c.html') }],
         [ "onDOMContentLoaded",
           { frameId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/d.html') }],
         [ "onErrorOccurred",
           { error: "net::ERR_FILE_NOT_FOUND",
             frameId: 1,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/c.html') }],
         [ "onCompleted",
           { frameId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/d.html') }]]);
       chrome.tabs.update(tabId, { url: getURL('iframeFail/d.html') });
     },
 
     /* An iframe navigates to a non-existant page. */
     function nonExistantIframeNavigation() {
       expect([
         [ "onBeforeNavigate",
           { frameId: 0,
             requestId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/a.html') }],
         [ "onCommitted",
           { frameId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             transitionQualifiers: "",
             transitionType: "link",
             url: getURL('iframeFail/a.html') }],
         [ "onBeforeNavigate",
           { frameId: 1,
             requestId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/b.html') }],
         [ "onDOMContentLoaded",
           { frameId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/a.html') }],
         [ "onCommitted",
           { frameId: 1,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             transitionQualifiers: "",
             transitionType: "auto_subframe",
             url: getURL('iframeFail/b.html') }],
         [ "onDOMContentLoaded",
           { frameId: 1,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/b.html') }],
         [ "onCompleted",
           { frameId: 1,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/b.html') }],
         [ "onCompleted",
           { frameId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/a.html') }],
         [ "onBeforeNavigate",
           { frameId: 1,
             requestId: 0,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/c.html') }],
         [ "onErrorOccurred",
           { error: "net::ERR_FILE_NOT_FOUND",
             frameId: 1,
-            tabId: tabId,
+            tabId: 0,
             timeStamp: 0,
             url: getURL('iframeFail/c.html') }]]);
       chrome.tabs.update(tabId, { url: getURL('iframeFail/a.html') });
     },
   ]);
 });
 </script>