Pepper/Flapper: Add IsFormatAvailable() to PPB_Flash_Clipboard.

webkit/tools/test_shell/mock_webclipboard_impl.cc

Index: webkit/tools/test_shell/mock_webclipboard_impl.cc
diff --git a/webkit/tools/test_shell/mock_webclipboard_impl.cc b/webkit/tools/test_shell/mock_webclipboard_impl.cc
index c10a32d9e1d5c8ecfe94fe9daeaeab4ffee37d6a..1e00f702f1a506f1204a52e8c3d02cbdfc14b95d 100644
--- a/webkit/tools/test_shell/mock_webclipboard_impl.cc
+++ b/webkit/tools/test_shell/mock_webclipboard_impl.cc
@@ -18,6 +18,9 @@ using WebKit::WebVector;
 
 bool MockWebClipboardImpl::isFormatAvailable(Format format, Buffer buffer) {
   switch (format) {
+    case FormatPlainText:
+      return !m_plainText.isEmpty();
+
     case FormatHTML:
       return !m_htmlText.isEmpty();