PDFs viewed inside a <webview> should navigate the same as PDFs in tabs.

chrome/browser/resources/pdf/pdf.js

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 'use strict';
 
 /**
  * @return {number} Width of a scrollbar in pixels
  */
 function getScrollbarWidth() {
@@ skipping 26 matching lines @@
       return filename;
     throw e;
   }
 }
 
 /**
  * Called when navigation happens in the current tab.
  * @param {string} url The url to be opened in the current tab.
  */
 function onNavigateInCurrentTab(url) {
-  // Prefer the tabs API because it can navigate from one file:// URL to
-  // another.
-  if (chrome.tabs)
-    chrome.tabs.update({url: url});
+  // When the PDFviewer is not inside a <webview>, prefer the tabs API because
+  // it can navigate from one file:// URL to another.
+  if (chrome.tabs && this.tabId_ != -1)
+    chrome.tabs.update(this.tabId_, {url: url});
   else
     window.location.href = url;
 }
 
 /**
  * Called when navigation happens in the new tab.
  * @param {string} url The url to be opened in the new tab.
  */
 function onNavigateInNewTab(url) {
   // Prefer the tabs API because it guarantees we can just open a new tab.
@@ skipping 50 matching lines @@
  * @param {!BrowserApi} browserApi An object providing an API to the browser.
  */
 function PDFViewer(browserApi) {
   this.browserApi_ = browserApi;
   this.loadState_ = LoadState.LOADING;
   this.parentWindow_ = null;
   this.parentOrigin_ = null;
 
   this.delayedScriptingMessages_ = [];
 
+  this.tabId_ = this.browserApi_.getStreamInfo().tabId;
   this.isPrintPreview_ = this.browserApi_.getStreamInfo().originalUrl.indexOf(
                              'chrome://print') == 0;
   this.isMaterial_ = location.pathname.substring(1) === 'index-material.html';
 
   // The sizer element is placed behind the plugin element to cause scrollbars
   // to be displayed in the window. It is sized according to the document size
   // of the pdf and zoom level.
   this.sizer_ = $('sizer');
   this.toolbar_ = $('toolbar');
   if (!this.isMaterial_ || this.isPrintPreview_)
@@ skipping 112 matching lines @@
   this.browserApi_.addZoomEventListener(
       this.zoomManager_.onBrowserZoomChange.bind(this.zoomManager_));
 
   // Setup the keyboard event listener.
   document.addEventListener('keydown', this.handleKeyEvent_.bind(this));
   document.addEventListener('mousemove', this.handleMouseEvent_.bind(this));
 
   // Parse open pdf parameters.
   this.paramsParser_ =
       new OpenPDFParamsParser(this.getNamedDestination_.bind(this));
-  this.navigator_ = new Navigator(this.browserApi_.getStreamInfo().originalUrl,
+  this.navigator_ = new Navigator(this.tabId_,
+                                  this.browserApi_.getStreamInfo().originalUrl,
                                   this.viewport_, this.paramsParser_,
                                   onNavigateInCurrentTab, onNavigateInNewTab);

[raymes, 2015/09/24 00:09:42]

can we bind the tabId to onNavigateInCurrentTab rather than passing it into
navigator?

   this.viewportScroller_ =
       new ViewportScroller(this.viewport_, this.plugin_, window);
 }
 
 PDFViewer.prototype = {
   /**
    * @private
    * Handle key events. These may come from the user directly or via the
    * scripting API.
    * @param {KeyboardEvent} e the event to handle.
@@ skipping 606 matching lines @@
    * Each bookmark is an Object containing a:
    * - title
    * - page (optional)
    * - array of children (themselves bookmarks)
    * @type {Array} the top-level bookmarks of the PDF.
    */
   get bookmarks() {
     return this.bookmarks_;
   }
 };