Fix "unused variable" warnings.

content/browser/renderer_host/text_input_client_message_filter.h

Index: content/browser/renderer_host/text_input_client_message_filter.h
diff --git a/content/browser/renderer_host/text_input_client_message_filter.h b/content/browser/renderer_host/text_input_client_message_filter.h
index 95780b055d8bb0e2b95a6009eba6c6d109d8f01a..e32743b0aa8ef29f4ec366aa61782223a8ec5c39 100644
--- a/content/browser/renderer_host/text_input_client_message_filter.h
+++ b/content/browser/renderer_host/text_input_client_message_filter.h
@@ -25,7 +25,7 @@ namespace content {
 class CONTENT_EXPORT TextInputClientMessageFilter
     : public BrowserMessageFilter {
  public:
-  explicit TextInputClientMessageFilter(int child_id);
+  TextInputClientMessageFilter();
 
   // BrowserMessageFilter override:
   bool OnMessageReceived(const IPC::Message& message) override;
@@ -44,9 +44,6 @@ class CONTENT_EXPORT TextInputClientMessageFilter
       const mac::AttributedStringCoder::EncodedString& string,
       const gfx::Point& point);
 
-  // Child process id.
-  int child_process_id_;
-
   DISALLOW_COPY_AND_ASSIGN(TextInputClientMessageFilter);
 };