Update to Chromium revision 12bfc336 (#338390).

- The ffmpeg library is now statically linked (see https://codereview.chromium.org/1141703002).
- Off-screen rendering of the PDF viewer does not work in combination with surfaces. Pass the
  `--disable-surfaces` command-line flag if GPU is enabled (see https://codereview.chromium.org/1169983006).

libcef/browser/extensions/extensions_api_client.cc

@@ -5,7 +5,13 @@
 
 #include "libcef/browser/extensions/extensions_api_client.h"
 
+#include "include/internal/cef_types_wrappers.h"
+#include "libcef/browser/extensions/extension_web_contents_observer.h"
 #include "libcef/browser/extensions/mime_handler_view_guest_delegate.h"
+#include "libcef/browser/extensions/pdf_web_contents_helper_client.h"
+#include "libcef/browser/printing/print_view_manager.h"
+
+#include "components/pdf/browser/pdf_web_contents_helper.h"
 
 namespace extensions {
 
@@ -25,4 +31,14 @@ CefExtensionsAPIClient::CreateMimeHandlerViewGuestDelegate(
   return make_scoped_ptr(new CefMimeHandlerViewGuestDelegate(guest));
 }
 
+void CefExtensionsAPIClient::AttachWebContentsHelpers(
+    content::WebContents* web_contents) const {
+  printing::PrintViewManager::CreateForWebContents(web_contents);
+  pdf::PDFWebContentsHelper::CreateForWebContentsWithClient(
+      web_contents,
+      scoped_ptr<pdf::PDFWebContentsHelperClient>(
+          new CefPDFWebContentsHelperClient()));
+  CefExtensionWebContentsObserver::CreateForWebContents(web_contents);
+}
+
 }  // namespace extensions