Add stubs and glue for routing a request for an image from the clipboard.

content/browser/renderer_host/clipboard_message_filter.cc

Index: content/browser/renderer_host/clipboard_message_filter.cc
diff --git a/content/browser/renderer_host/clipboard_message_filter.cc b/content/browser/renderer_host/clipboard_message_filter.cc
index 8cb3b9d620a11d2857b09d2d7a8248e52d927a52..ca71e5dcb6cd956745547e653b4e1a139e0c4add 100644
--- a/content/browser/renderer_host/clipboard_message_filter.cc
+++ b/content/browser/renderer_host/clipboard_message_filter.cc
@@ -38,7 +38,9 @@ ClipboardMessageFilter::ClipboardMessageFilter() {
 void ClipboardMessageFilter::OverrideThreadForMessage(
     const IPC::Message& message, BrowserThread::ID* thread) {
 #if defined(USE_X11)
-  if (IPC_MESSAGE_CLASS(message) == ClipboardMsgStart)
+  if (message.type() == ClipboardHostMsg_ReadImage::ID)
+    *thread = BrowserThread::BACKGROUND_X11;
+  else if (IPC_MESSAGE_CLASS(message) == ClipboardMsgStart)
     *thread = BrowserThread::UI;
 #endif
 }
@@ -53,6 +55,7 @@ bool ClipboardMessageFilter::OnMessageReceived(const IPC::Message& message,
     IPC_MESSAGE_HANDLER(ClipboardHostMsg_ReadText, OnReadText)
     IPC_MESSAGE_HANDLER(ClipboardHostMsg_ReadAsciiText, OnReadAsciiText)
     IPC_MESSAGE_HANDLER(ClipboardHostMsg_ReadHTML, OnReadHTML)
+    IPC_MESSAGE_HANDLER(ClipboardHostMsg_ReadImage, OnReadImage)
 #if defined(OS_MACOSX)
     IPC_MESSAGE_HANDLER(ClipboardHostMsg_FindPboardWriteStringAsync,
                         OnFindPboardWriteString)
@@ -132,6 +135,11 @@ void ClipboardMessageFilter::OnReadHTML(
   *url = GURL(src_url_str);
 }
 
+void ClipboardMessageFilter::OnReadImage(
+    ui::Clipboard::Buffer buffer, std::string* data) {
+  GetClipboard()->ReadImage(buffer, data);
+}
+
 void ClipboardMessageFilter::OnReadAvailableTypes(
     ui::Clipboard::Buffer buffer, bool* succeeded, std::vector<string16>* types,
     bool* contains_filenames) {