Refactor the loading tracking logic in WebContentsImpl.

content/browser/frame_host/frame_tree_node.h

Index: content/browser/frame_host/frame_tree_node.h
diff --git a/content/browser/frame_host/frame_tree_node.h b/content/browser/frame_host/frame_tree_node.h
index 5d0a34bd366fd3875a632891acc18ac624c64080..d6a4bdb879c17c7e1e6d5a79eaf384a0e103ee4b 100644
--- a/content/browser/frame_host/frame_tree_node.h
+++ b/content/browser/frame_host/frame_tree_node.h
@@ -24,6 +24,13 @@ class FrameTree;
 class Navigator;
 class RenderFrameHostImpl;
 
+// These values indicate the loading progress status.
+// The minimum progress vlaue matches what Blink's ProgressTracker has

[clamy, 2015/02/16 14:20:59]

nit: s/vlaue/value
Also I don't think that a line return is necessary here.

[Fabrice (no longer in Chrome), 2015/02/20 12:58:58]

Done.

+// traditionally used for a minimum progress value.
+const double kNotStartedLoadingProgress = 0.0;

[clamy, 2015/02/16 14:20:59]

So I've found an example of const values in the code at
https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/fr...
. I think we should try to match that here.

[Fabrice (no longer in Chrome), 2015/02/20 12:58:58]

Done.

+const double kMinimumLoadingProgress = 0.1;
+const double kDoneLoadingProgress = 1.0;
+
 // When a page contains iframes, its renderer process maintains a tree structure
 // of those frames. We are mirroring this tree in the browser process. This
 // class represents a node in this tree and is a wrapper for all objects that
@@ -108,10 +115,17 @@ class CONTENT_EXPORT FrameTreeNode {
   void set_is_loading(bool is_loading) {
     is_loading_ = is_loading;
   }
+
   bool is_loading() const {
     return is_loading_;
   }
 
+  void set_loading_progress(double loading_progress) {
+    loading_progress_ = loading_progress;
+  }
+
+  double get_loading_progress() const { return loading_progress_; }
+
   RenderFrameHostImpl* current_frame_host() const {
     return render_manager_.current_frame_host();
   }
@@ -167,6 +181,9 @@ class CONTENT_EXPORT FrameTreeNode {
   // RenderFrameHost or using a counter to balance the events out.
   bool is_loading_;
 
+  // Double value representing the frame's completion progress (from 0 to 1).
+  double loading_progress_;
+
   DISALLOW_COPY_AND_ASSIGN(FrameTreeNode);
 };