Remove WebContents::InsertCSS since it is unused

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 621712eba762c597a3c04f315aa8afee9afe1be3..c84cb1d7117497351734b599300be905b57ad33c 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -1523,7 +1523,6 @@ bool RenderFrameImpl::OnMessageReceived(const IPC::Message& msg) {
                         OnSetEditableSelectionOffsets)
     IPC_MESSAGE_HANDLER(InputMsg_ExecuteNoValueEditCommand,
                         OnExecuteNoValueEditCommand)
-    IPC_MESSAGE_HANDLER(FrameMsg_CSSInsertRequest, OnCSSInsertRequest)
     IPC_MESSAGE_HANDLER(FrameMsg_AddMessageToConsole, OnAddMessageToConsole)
     IPC_MESSAGE_HANDLER(FrameMsg_JavaScriptExecuteRequest,
                         OnJavaScriptExecuteRequest)
@@ -1915,10 +1914,6 @@ void RenderFrameImpl::OnSaveImageAt(int x, int y) {
   frame_->saveImageAt(WebPoint(x, y));
 }
 
-void RenderFrameImpl::OnCSSInsertRequest(const std::string& css) {
-  frame_->document().insertStyleSheet(WebString::fromUTF8(css));
-}
-
 void RenderFrameImpl::OnAddMessageToConsole(ConsoleMessageLevel level,
                                             const std::string& message) {
   AddMessageToConsole(level, message);