Introduce browser side FrameTreeNodeBlameContext

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 d38185808db2c6eb11f4130ed031e24a5b72a7c2..15df53db42c4281c646a4873951918faa3b47320 100644
--- a/content/browser/frame_host/frame_tree_node.h
+++ b/content/browser/frame_host/frame_tree_node.h
@@ -13,6 +13,7 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "content/browser/frame_host/frame_tree_node_blame_context.h"
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/browser/frame_host/render_frame_host_manager.h"
 #include "content/common/content_export.h"
@@ -265,13 +266,19 @@ class CONTENT_EXPORT FrameTreeNode {
   // FrameTreeNode.
   void BeforeUnloadCanceled();
 
+  // Creates and initializes a new FrameTreeNodeBlameContext for tracing
+  // snapshots of this node and attributing browser process activities to it.
+  void InitializeBlameContext();
+
+  FrameTreeNodeBlameContext* blame_context() const {
+    return blame_context_.get();
+  }
+
  private:
   class OpenerDestroyedObserver;
 
   void set_parent(FrameTreeNode* parent) { parent_ = parent; }
 
-  void TraceSnapshot() const;
-
   // The next available browser-global FrameTreeNode ID.
   static int next_frame_tree_node_id_;
 
@@ -347,6 +354,12 @@ class CONTENT_EXPORT FrameTreeNode {
 
   base::TimeTicks last_focus_time_;
 
+  // The FrameTreeNodeBlameContext object for tracing the snapshots of this
+  // FrameTreeNode and attributing browser process activities to this node
+  // (when possible).  It is unrelated to the core logic of FrameTreeNode.
+  // See frame_tree_node_blame_context.h for more detailed documentation.
+  std::unique_ptr<FrameTreeNodeBlameContext> blame_context_;
+
   DISALLOW_COPY_AND_ASSIGN(FrameTreeNode);
 };