Make NavigationParams clearer

content/common/navigation_params.h

Index: content/common/navigation_params.h
diff --git a/content/common/navigation_params.h b/content/common/navigation_params.h
index 9b3fccf4ab78e61b656a68d5e077f0c0a1611989..ce34bcc04bdf1d7f7bab3adab382715c5587b28f 100644
--- a/content/common/navigation_params.h
+++ b/content/common/navigation_params.h
@@ -21,12 +21,13 @@ class RefCountedMemory;
 }
 
 namespace content {
-class NavigationEntry;
 
 // The following structures hold parameters used during a navigation. In
 // particular they are used by FrameMsg_Navigate, FrameMsg_CommitNavigation and
 // FrameHostMsg_BeginNavigation.
 
+// Provided by the browser or the renderer -------------------------------------
+
 // Used by all navigation IPCs.
 struct CONTENT_EXPORT CommonNavigationParams {
   CommonNavigationParams();
@@ -76,7 +77,15 @@ struct CONTENT_EXPORT CommonNavigationParams {
   GURL history_url_for_data_url;
 };
 
-// PlzNavigate: parameters needed to start a navigation on the IO thread.
+// Provided by the renderer ----------------------------------------------------
+//
+// This struct holds parameters sent by the renderer to the browser. It is only
+// used in PlzNavigate (since in the current architecture, the renderer does not
+// inform the browser of navigations until they commit).
+
+// This struct is not used outside of the PlzNavigate project.
+// PlzNavigate: parameters needed to start a navigation on the IO thread,
+// following a renderer-initiated navigation request.
 struct CONTENT_EXPORT BeginNavigationParams {
   // TODO(clamy): See if it is possible to reuse this in
   // ResourceMsg_Request_Params.
@@ -99,17 +108,73 @@ struct CONTENT_EXPORT BeginNavigationParams {
   bool has_user_gesture;
 };
 
-// Used by FrameMsg_Navigate.
-// PlzNavigate: sent to the renderer when the navigation is ready to commit.
-struct CONTENT_EXPORT CommitNavigationParams {
-  CommitNavigationParams();
-  CommitNavigationParams(bool is_overriding_user_agent,
-                         base::TimeTicks navigation_start,
-                         const std::vector<GURL>& redirects,
-                         bool can_load_local_resources,
-                         const std::string& frame_to_navigate,
-                         base::Time request_time);
-  ~CommitNavigationParams();
+// Provided by the browser -----------------------------------------------------
+//
+// These structs are sent by the browser to the renderer to start/commit a
+// navigation depending on whether browser-side navigation is enabled.
+// Parameters used both in the current architecture and PlzNavigate should be
+// put in RequestNavigationParams.  Parameters only used by the current
+// architecture should go in StartNavigationParams.
+
+// Used by FrameMsg_Navigate. Holds the parameters needed by the renderer to
+// start a browser-initiated navigation besides those in CommonNavigationParams.
+// The difference with the RequestNavigationParams below is that they are only
+// used in the current architecture of navigation, and will not be used by
+// PlzNavigate.
+// PlzNavigate: These are not used.
+struct CONTENT_EXPORT StartNavigationParams {
+  StartNavigationParams();
+  StartNavigationParams(
+      bool is_post,
+      const std::string& extra_headers,
+      const std::vector<unsigned char>& browser_initiated_post_data,
+      bool should_replace_current_entry,
+      int transferred_request_child_id,
+      int transferred_request_request_id);
+  ~StartNavigationParams();
+
+  // Whether the navigation is a POST request (as opposed to a GET).
+  bool is_post;
+
+  // Extra headers (separated by \n) to send during the request.
+  std::string extra_headers;
+
+  // If is_post is true, holds the post_data information from browser. Empty
+  // otherwise.
+  std::vector<unsigned char> browser_initiated_post_data;
+
+  // Informs the RenderView the pending navigation should replace the current
+  // history entry when it commits. This is used for cross-process redirects so
+  // the transferred navigation can recover the navigation state.
+  bool should_replace_current_entry;
+
+  // The following two members identify a previous request that has been
+  // created before this navigation is being transferred to a new render view.
+  // This serves the purpose of recycling the old request.
+  // Unless this refers to a transferred navigation, these values are -1 and -1.
+  int transferred_request_child_id;
+  int transferred_request_request_id;
+};
+
+// Used by FrameMsg_Navigate. Holds the parameters needed by the renderer to
+// start a browser-initiated navigation besides those in CommonNavigationParams.
+// PlzNavigate: sent to the renderer to make it issue a stream request for a
+// navigation that is ready to commit.
+struct CONTENT_EXPORT RequestNavigationParams {
+  RequestNavigationParams();
+  RequestNavigationParams(bool is_overriding_user_agent,
+                          base::TimeTicks navigation_start,
+                          const std::vector<GURL>& redirects,
+                          bool can_load_local_resources,
+                          const std::string& frame_to_navigate,
+                          base::Time request_time,
+                          const PageState& page_state,
+                          int32 page_id,
+                          int pending_history_list_offset,
+                          int current_history_list_offset,
+                          int current_history_list_length,
+                          bool should_clear_history_list);
+  ~RequestNavigationParams();
 
   // Whether or not the user agent override string should be used.
   bool is_overriding_user_agent;
@@ -132,19 +197,6 @@ struct CONTENT_EXPORT CommitNavigationParams {
   // infrastructure to set up DocumentState associated with the RenderView.
   // TODO(ppi): make it go away.
   base::Time request_time;
-};
-
-// Used by FrameMsg_Navigate.
-// PlzNavigate: sent to the renderer when the navigation is ready to commit.
-struct CONTENT_EXPORT HistoryNavigationParams {
-  HistoryNavigationParams();
-  HistoryNavigationParams(const PageState& page_state,
-                          int32 page_id,
-                          int pending_history_list_offset,
-                          int current_history_list_offset,
-                          int current_history_list_length,
-                          bool should_clear_history_list);
-  ~HistoryNavigationParams();
 
   // Opaque history state (received by ViewHostMsg_UpdateState).
   PageState page_state;
@@ -170,54 +222,19 @@ struct CONTENT_EXPORT HistoryNavigationParams {
   bool should_clear_history_list;
 };
 
-// Parameters needed at the start of a navigation. Used by FrameMsg_Navigate.
-// PlzNavigate: these parameters are not used in navigation.
-struct CONTENT_EXPORT StartNavigationParams {
-  StartNavigationParams();
-  StartNavigationParams(
-      bool is_post,
-      const std::string& extra_headers,
-      const std::vector<unsigned char>& browser_initiated_post_data,
-      bool should_replace_current_entry,
-      int transferred_request_child_id,
-      int transferred_request_request_id);
-  ~StartNavigationParams();
-
-  // Whether the navigation is a POST request (as opposed to a GET).
-  bool is_post;
-
-  // Extra headers (separated by \n) to send during the request.
-  std::string extra_headers;
-
-  // If is_post is true, holds the post_data information from browser. Empty
-  // otherwise.
-  std::vector<unsigned char> browser_initiated_post_data;
-
-  // Informs the RenderView the pending navigation should replace the current
-  // history entry when it commits. This is used for cross-process redirects so
-  // the transferred navigation can recover the navigation state.
-  bool should_replace_current_entry;
-
-  // The following two members identify a previous request that has been
-  // created before this navigation is being transferred to a new render view.
-  // This serves the purpose of recycling the old request.
-  // Unless this refers to a transferred navigation, these values are -1 and -1.
-  int transferred_request_child_id;
-  int transferred_request_request_id;
-};
-
+// Helper struct keeping track in one place of all the parameters the browser
+// needs to provide to the renderer.
 struct NavigationParams {
   NavigationParams(const CommonNavigationParams& common_params,
                    const StartNavigationParams& start_params,
-                   const CommitNavigationParams& commit_params,
-                   const HistoryNavigationParams& history_params);
+                   const RequestNavigationParams& request_params);
   ~NavigationParams();
 
   CommonNavigationParams common_params;
   StartNavigationParams start_params;
-  CommitNavigationParams commit_params;
-  HistoryNavigationParams history_params;
+  RequestNavigationParams request_params;
 };
+
 }  // namespace content
 
 #endif  // CONTENT_COMMON_NAVIGATION_PARAMS_H_