chrome: Cleanup class/struct forward declarations

chrome/browser/renderer_host/chrome_render_message_filter.h

Index: chrome/browser/renderer_host/chrome_render_message_filter.h
diff --git a/chrome/browser/renderer_host/chrome_render_message_filter.h b/chrome/browser/renderer_host/chrome_render_message_filter.h
index 40175c713cb291ff8b8daaa2a2adc2a5afe382ef..c00c9c4e066f94389c0bb33487d8a59c308443c5 100644
--- a/chrome/browser/renderer_host/chrome_render_message_filter.h
+++ b/chrome/browser/renderer_host/chrome_render_message_filter.h
@@ -38,10 +38,6 @@ namespace network_hints {
 struct LookupRequest;
 }
 
-namespace extensions {
-class InfoMap;
-}
-
 // This class filters out incoming Chrome-specific IPC messages for the renderer
 // process on the IPC thread.
 class ChromeRenderMessageFilter : public content::BrowserMessageFilter {