Introduce webNavigation.onTabReplaced event that is fired when a tab from instant or prerender repl…

chrome/common/extensions/docs/static/webNavigation.html

Index: chrome/common/extensions/docs/static/webNavigation.html
diff --git a/chrome/common/extensions/docs/static/webNavigation.html b/chrome/common/extensions/docs/static/webNavigation.html
index dd0545d7ad0f68a989db160e9f00de14b2cb42e1..3dbbd8060e862aa644256f334629f3f2cf1ea6dd 100644
--- a/chrome/common/extensions/docs/static/webNavigation.html
+++ b/chrome/common/extensions/docs/static/webNavigation.html
@@ -59,6 +59,14 @@ If the reference fragment of a frame is changed, a
 time after <code>onDOMContentLoaded</code>, even after
 <code>onCompleted</code>.
 </p>
+<p>
+If a navigation was triggered via <a
+href="https://support.google.com/chrome/bin/answer.py?answer=177873">Chrome
+Instant</a> or <a
+href="https://support.google.com/chrome/bin/answer.py?answer=1385029">Instant
+Pages</a>, a completely loaded page is swapped into the current tab. In that
+case, an <code>onTabReplaced</code> event is fired.
+</p>
 
 <h2>Relation to webRequest events</h2>
 <p>
@@ -74,6 +82,16 @@ state that is displayed in the UI, while the webRequest events correspond to
 the state of the network stack which is generally opaque to the user.
 </p>
 
+<h2>A note about tab IDs</h2>
+<p>
+Not all navigating tabs correspond to actual tabs in Chrome's UI, e.g., a tab
+that is being pre-rendered. Such tabs are not accessible via the
+<a href="tabs.html">tabs API</a> nor can you request information about them via
+<code>webNavigation.getFrame</code> or <code>webNavigation.getAllFrames</code>.
+Once such a tab is swapped in, an <code>onTabReplaced</code> event is fired and
+they become accessible via these APIs.
+</p>
+
 <h2>A note about timestamps</h2>
 <p>
 It's important to note that some technical oddities in the OS's handling