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

chrome/browser/resources/pdf/navigator.js

Index: chrome/browser/resources/pdf/navigator.js
diff --git a/chrome/browser/resources/pdf/navigator.js b/chrome/browser/resources/pdf/navigator.js
index e6bd7ad28c4531d2fe846a35ae0cc0cdd0cea6fa..6ce5edde23d1adbb91fa26a601e7c84b583a2ad3 100644
--- a/chrome/browser/resources/pdf/navigator.js
+++ b/chrome/browser/resources/pdf/navigator.js
@@ -6,6 +6,7 @@
 
 /**
  * Creates a new Navigator for navigating to links inside or outside the PDF.
+ * @param {int} tabId of browser tab containing viewer, -1 if in <webview>
  * @param {string} originalUrl The original page URL.
  * @param {Object} viewport The viewport info of the page.
  * @param {Object} paramsParser The object for URL parsing.
@@ -14,11 +15,13 @@
  * @param {Function} navigateInNewTabCallback The Callback function that gets
  *    called when navigation happens in the new tab.
  */
-function Navigator(originalUrl,
+function Navigator(tabId,
+                   originalUrl,
                    viewport,
                    paramsParser,
                    navigateInCurrentTabCallback,
                    navigateInNewTabCallback) {
+  this.tabId_ = tabId;
   this.originalUrl_ = originalUrl;
   this.viewport_ = viewport;
   this.paramsParser_ = paramsParser;