Remove old prefetcher histogram code in render_frame_impl

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 7f7349ab3265b2251098e10c728cdc2ea33885c5..478cd280a421f866e0e9c7806f154eedf3a911a7 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -3092,33 +3092,6 @@ void RenderFrameImpl::didCreateDataSource(blink::WebLocalFrame* frame,
   UpdateNavigationState(document_state, false /* was_within_same_page */,
                         content_initiated);
 
-  // DocumentState::referred_by_prefetcher_ is true if we are
-  // navigating from a page that used prefetching using a link on that
-  // page.  We are early enough in the request process here that we
-  // can still see the DocumentState of the previous page and set
-  // this value appropriately.
-  // TODO(gavinp): catch the important case of navigation in a new
-  // renderer process.
-  if (webview) {
-    if (WebFrame* old_frame = webview->mainFrame()) {
-      const WebURLRequest& original_request = datasource->originalRequest();
-      const GURL referrer(blink::WebStringToGURL(
-          original_request.httpHeaderField(WebString::fromUTF8("Referer"))));
-      if (!referrer.is_empty() && old_frame->isWebLocalFrame() &&
-          DocumentState::FromDataSource(old_frame->dataSource())
-              ->was_prefetcher()) {
-        for (; old_frame; old_frame = old_frame->traverseNext(false)) {
-          WebDataSource* old_frame_datasource = old_frame->dataSource();
-          if (old_frame_datasource &&
-              referrer == GURL(old_frame_datasource->request().url())) {
-            document_state->set_was_referred_by_prefetcher(true);
-            break;
-          }
-        }
-      }
-    }
-  }
-
   if (content_initiated) {
     const WebURLRequest& request = datasource->request();
     switch (request.getCachePolicy()) {
@@ -4090,19 +4063,6 @@ void RenderFrameImpl::willSendRequest(blink::WebLocalFrame* frame,
     }
   }
 
-  // TODO(creis): Update prefetching to work with out-of-process iframes.
-  WebFrame* top_frame = frame->top();
-  if (top_frame && top_frame->isWebLocalFrame()) {
-    DocumentState* top_document_state =
-        DocumentState::FromDataSource(top_frame->dataSource());
-    if (top_document_state) {
-      // TODO(gavinp): separate out prefetching and prerender field trials
-      // if the rel=prerender rel type is sticking around.
-      if (request.getRequestContext() == WebURLRequest::RequestContextPrefetch)
-        top_document_state->set_was_prefetcher(true);
-    }
-  }
-
   // This is an instance where we embed a copy of the routing id
   // into the data portion of the message. This can cause problems if we
   // don't register this id on the browser side, since the download manager