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 23 matching lines @@
     return decodeURIComponent(filename);
   } catch (e) {
     if (e instanceof URIError)
       return filename;
     throw e;
   }
 }
 
 /**
  * Called when navigation happens in the current tab.
+ * @param {number} tabId The id of the current tab; -1 if no 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});
+function onNavigateInCurrentTab(tabId, 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 && tabId != -1)

[Dan Beam, 2015/09/28 15:59:11]

are you using tabId == -1 basically as a check to see if you're embedded in a
<webview>?  because if so...

  /**
   * @param {string} url ...
   * @param {boolean} inWebView ...
   */
  function onNavigateInCurrentTab(url, inWebView) {
    if (!inWebView && chrome.tabs)
      chrome.tabs.update({url: url});
    else
      window.location.href = url;
  }

[wjmaclean, 2015/09/28 16:10:09]

We could change it to 

@param {boolean} inTab

perhaps? I don't think we should limit ourselves to just WebView in this case.

[raymes, 2015/09/29 01:46:27]

I agree - there might be other cases where we don't have a tabId. sammc@ would
know about what the other cases are.

+    chrome.tabs.update(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 184 matching lines @@
 
   // 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.viewport_, this.paramsParser_,
-                                  onNavigateInCurrentTab, onNavigateInNewTab);
+                                  onNavigateInCurrentTab.bind(undefined,
+                                      this.browserApi_.getStreamInfo().tabId),

[Dan Beam, 2015/09/28 15:59:12]

wait, don't you *want* this to use the current tabId if it changes?

[wjmaclean, 2015/09/28 16:10:08]

Well, yes, I think we would. However, it's not at all obvious that a Navigator,
once created, will ever change its tabId. I was assuming from Raymes suggestion
that we don't think it ever will.

[raymes, 2015/09/29 01:46:27]

Correct - the tabId will never change.

+                                  onNavigateInNewTab);
   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_;
   }
 };