Fix crash in PDF accessibility when PDF engine reports -1 as char count.

chrome/browser/pdf/pdf_extension_test.cc

 // Copyright 2014 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.
 
 #include <stddef.h>
 
 #include <vector>
 
 #include "base/base_paths.h"
 #include "base/files/file_enumerator.h"
@@ skipping 641 matching lines @@
   content::WebContents* guest_contents = LoadPdfGetGuestContents(test_pdf_url);
   ASSERT_TRUE(guest_contents);
 
   WaitForAccessibilityTreeToContainNodeWithName(guest_contents,
                                                 "1 First Section\r\n");
   ui::AXTreeUpdate ax_tree = GetAccessibilityTreeSnapshot(guest_contents);
   std::string ax_tree_dump = DumpPdfAccessibilityTree(ax_tree);
   ASSERT_MULTILINE_STREQ(kExpectedPDFAXTree, ax_tree_dump);
 }
 
+#if defined(GOOGLE_CHROME_BUILD)
+// Test a particular PDF encountered in the wild that encountered a crash

[raymes, 2017/01/30 18:58:04]

nit: encountered  a crash->triggered a crash

+// when accessibility is enabled.  (http://crbug.com/648981)
+IN_PROC_BROWSER_TEST_F(PDFExtensionTest, PdfAccessibilityCharCountCrash) {
+  content::BrowserAccessibilityState::GetInstance()->EnableAccessibility();
+  GURL test_pdf_url(embedded_test_server()->GetURL(
+      "/pdf_private/accessibility_crash_1.pdf"));
+
+  content::WebContents* guest_contents = LoadPdfGetGuestContents(test_pdf_url);
+  ASSERT_TRUE(guest_contents);
+
+  WaitForAccessibilityTreeToContainNodeWithName(guest_contents, "Page 1");
+}
+#endif
+
 IN_PROC_BROWSER_TEST_F(PDFExtensionTest, PdfAccessibilityEnableLater) {
   // In this test, load the PDF file first, with accessibility off.
   GURL test_pdf_url(embedded_test_server()->GetURL("/pdf/test-bookmarks.pdf"));
   content::WebContents* guest_contents = LoadPdfGetGuestContents(test_pdf_url);
   ASSERT_TRUE(guest_contents);
 
   // Now enable accessibility globally, and assert that the PDF accessibility
   // tree loads.
   EnableAccessibilityForWebContents(guest_contents);
   WaitForAccessibilityTreeToContainNodeWithName(guest_contents,
@@ skipping 318 matching lines @@
   ASSERT_EQ(web_contents, active_web_contents);
 
   content::WebContents* new_web_contents =
       browser()->tab_strip_model()->GetWebContentsAt(1);
   ASSERT_TRUE(new_web_contents);
   ASSERT_NE(web_contents, new_web_contents);
 
   const GURL& url = new_web_contents->GetURL();
   ASSERT_EQ(GURL("http://www.example.com"), url);
 }