Try 2 - Change how ui::Clipboard is accessed so there's only one per thread.

chrome/browser/ui/pdf/pdf_browsertest.cc

 // Copyright (c) 2012 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 "base/file_util.h"
 #include "base/path_service.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/ui/browser.h"
@@ skipping 251 matching lines @@
 #define MAYBE_FindAndCopy FindAndCopy
 #endif
 IN_PROC_BROWSER_TEST_F(PDFBrowserTest, MAYBE_FindAndCopy) {
   ASSERT_NO_FATAL_FAILURE(Load());
   // Verifies that find in page works.
   ASSERT_EQ(3, ui_test_utils::FindInPage(
       chrome::GetActiveTabContents(browser()), UTF8ToUTF16("adipiscing"),
       true, false, NULL, NULL));
 
   // Verify that copying selected text works.
-  ui::Clipboard clipboard;
+  ui::Clipboard* clipboard = ui::Clipboard::GetForCurrentThread();
   // Reset the clipboard first.
   ui::Clipboard::ObjectMap objects;
   ui::Clipboard::ObjectMapParams params;
   params.push_back(std::vector<char>());
   objects[ui::Clipboard::CBF_TEXT] = params;
-  clipboard.WriteObjects(ui::Clipboard::BUFFER_STANDARD, objects);
+  clipboard->WriteObjects(ui::Clipboard::BUFFER_STANDARD, objects);
 
   chrome::GetActiveWebContents(browser())->GetRenderViewHost()->Copy();
   ASSERT_NO_FATAL_FAILURE(WaitForResponse());
 
-
   std::string text;
-  clipboard.ReadAsciiText(ui::Clipboard::BUFFER_STANDARD, &text);
+  clipboard->ReadAsciiText(ui::Clipboard::BUFFER_STANDARD, &text);
   ASSERT_EQ("adipiscing", text);
 }
 
 // Tests that loading async pdfs works correctly (i.e. document fully loads).
 // This also loads all documents that used to crash, to ensure we don't have
 // regressions.
 // If it flakes, reopen http://crbug.com/74548.
 IN_PROC_BROWSER_TEST_F(PDFBrowserTest, SLOW_Loading) {
   ASSERT_TRUE(pdf_test_server()->Start());
 
@@ skipping 94 matching lines @@
       chrome::GetActiveWebContents(browser())->GetRenderViewHost(),
       std::wstring(),
       L"reloadPDF();"));
   observer.Wait();
 
   ASSERT_EQ("success",
             chrome::GetActiveWebContents(browser())->GetURL().query());
 }
 
 }  // namespace