Add page load metrics for no-store forward back navigations.

content/public/browser/navigation_handle.h

Index: content/public/browser/navigation_handle.h
diff --git a/content/public/browser/navigation_handle.h b/content/public/browser/navigation_handle.h
index ff190a757cd2be4cdc147e72aa5367cdf71e8fa8..007cd9da717135ea9779f9b1bb015445b4a2f6a8 100644
--- a/content/public/browser/navigation_handle.h
+++ b/content/public/browser/navigation_handle.h
@@ -15,6 +15,10 @@
 
 class GURL;
 
+namespace net {
+class HttpResponseHeaders;
+}  // namespace net
+
 namespace content {
 class NavigationData;
 class NavigationThrottle;
@@ -150,6 +154,12 @@ class CONTENT_EXPORT NavigationHandle {
   // Whether the navigation resulted in an error page.
   virtual bool IsErrorPage() = 0;
 
+  // Returns the response headers for the request or nullptr if there are none.
+  // This should only be accessed after a redirect was encountered or after the
+  // navigation is ready to commit. The headers returned should not be modified,
+  // as modifications will not be reflected in the network stack.
+  virtual const net::HttpResponseHeaders* GetResponseHeaders() = 0;
+
   // Resumes a navigation that was previously deferred by a NavigationThrottle.
   virtual void Resume() = 0;