Remove support for the keygen tag

content/renderer/renderer_blink_platform_impl.h

Index: content/renderer/renderer_blink_platform_impl.h
diff --git a/content/renderer/renderer_blink_platform_impl.h b/content/renderer/renderer_blink_platform_impl.h
index 9c41bdc0ace3c6a6863fe626c8186f0eebba3c30..6c9ac6633ab6de62f4c152cdc8d325c2766a887a 100644
--- a/content/renderer/renderer_blink_platform_impl.h
+++ b/content/renderer/renderer_blink_platform_impl.h
@@ -116,11 +116,6 @@ class CONTENT_EXPORT RendererBlinkPlatformImpl : public BlinkPlatformImpl {
       const blink::WebSecurityOrigin& origin) override;
   cc::FrameSinkId generateFrameSinkId() override;
 
-  blink::WebString signedPublicKeyAndChallengeString(
-      unsigned key_size_index,
-      const blink::WebString& challenge,
-      const blink::WebURL& url,
-      const blink::WebURL& top_origin) override;
   void getPluginList(bool refresh,
                      const blink::WebSecurityOrigin& mainFrameOrigin,
                      blink::WebPluginListBuilder* builder) override;