[reland] Change net's predictor_tab_helper to use the new content Navigation API

chrome/browser/net/predictor_tab_helper.cc

Index: chrome/browser/net/predictor_tab_helper.cc
diff --git a/chrome/browser/net/predictor_tab_helper.cc b/chrome/browser/net/predictor_tab_helper.cc
index a6f59ba2f947eb775eec68ea6fe52e6d787ea772..b0856d5c72f65ff9952d427a2196c34144bdb368 100644
--- a/chrome/browser/net/predictor_tab_helper.cc
+++ b/chrome/browser/net/predictor_tab_helper.cc
@@ -4,32 +4,60 @@
 
 #include "chrome/browser/net/predictor_tab_helper.h"
 
-#include "base/command_line.h"
+#include "base/feature_list.h"
 #include "chrome/browser/net/predictor.h"
 #include "chrome/browser/profiles/profile.h"
-#include "chrome/common/chrome_switches.h"
 #include "chrome/common/url_constants.h"
+#include "content/public/browser/navigation_handle.h"
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(chrome_browser_net::PredictorTabHelper);
 
 namespace chrome_browser_net {
 
+namespace {
+
+// Triggers the preconnector on the new navigation api. This captures more
+// navigations.
+const base::Feature kPreconnectMore{"PreconnectMore",
+                                    base::FEATURE_DISABLED_BY_DEFAULT};
+
+}  // namespace
+
 PredictorTabHelper::PredictorTabHelper(content::WebContents* web_contents)
-    : content::WebContentsObserver(web_contents) {
+    : content::WebContentsObserver(web_contents),
+      predicted_from_pending_entry_(false) {
 }
 
 PredictorTabHelper::~PredictorTabHelper() {
 }
 
+void PredictorTabHelper::DidStartNavigation(
+    content::NavigationHandle* navigation_handle) {
+  if (predicted_from_pending_entry_) {

[Charlie Harrison, 2016/04/08 12:16:49]

Staring at this, I think this if statement should go below the check for
subframe navigations. This approach means

1. Type facebook.com (DidStartNavigationToPendingEntry)
2. A racy subframe navigation in the tab occurs
3. facebook.com didStartProvisionalLoad received from (1)

The racy subframe nav will uncheck the |predicted_from_pending_entry_bit_|. I'll
change this in my next patch set.

+    predicted_from_pending_entry_ = false;
+    return;
+  }
+  if (!base::FeatureList::IsEnabled(kPreconnectMore))
+    return;
+  // Subframe navigations are handled in WitnessURLRequest.
+  if (!navigation_handle->IsInMainFrame())
+    return;
+  PreconnectUrl(navigation_handle->GetURL());
+}
+
 void PredictorTabHelper::DidStartNavigationToPendingEntry(
     const GURL& url,
     content::NavigationController::ReloadType reload_type) {
+  // The standard way to preconnect based on navigation.
+  PreconnectUrl(url);
+  predicted_from_pending_entry_ = true;
+}
+
+void PredictorTabHelper::PreconnectUrl(const GURL& url) {
   Profile* profile =
       Profile::FromBrowserContext(web_contents()->GetBrowserContext());
   chrome_browser_net::Predictor* predictor = profile->GetNetworkPredictor();
-  if (!predictor)
-    return;
-  if (url.SchemeIs(url::kHttpScheme) || url.SchemeIs(url::kHttpsScheme))
+  if (predictor && url.SchemeIsHTTPOrHTTPS())
     predictor->PreconnectUrlAndSubresources(url, GURL());
 }