Introduce browser side FrameTreeNodeBlameContext

content/browser/frame_host/frame_tree_node_blame_context.h

Index: content/browser/frame_host/frame_tree_node_blame_context.h
diff --git a/content/browser/frame_host/frame_tree_node_blame_context.h b/content/browser/frame_host/frame_tree_node_blame_context.h
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index 0000000000000000000000000000000000000000..a50ac52bb9fa5c93a3e6e2cd805d225e77fee3cf
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+++ b/content/browser/frame_host/frame_tree_node_blame_context.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_NODE_BLAME_CONTEXT_H
+#define CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_NODE_BLAME_CONTEXT_H
+
+#include "base/macros.h"
+#include "base/synchronization/lock.h"
+#include "base/trace_event/blame_context.h"
+#include "url/gurl.h"
+
+namespace base {
+namespace trace_event {
+class TracedValue;
+}
+}
+
+namespace content {
+
+class FrameTreeNode;
+
+// FrameTreeNodeBlameContext is a helper class for tracing snapshots of each
+// FrameTreeNode and attributing browser activities to frames (when possible),
+// in the framework of FrameBlamer (crbug.com/546021).
+//
+//
+// *** LIFECYCLE ***
+//
+// Each FrameTreeNodeBlameContext is owned by a FrameTreeNode, and each
+// FrameTreeNode owns at most one FrameTreeNodeBlameContext.  The lifecycle
+// of each FrameTreeNodeBlameContext is managed by its owner node.
+// Creation: For each root FrameTreeNode, its blame context is created right
+// after the node's intialization.  For each other node, its blame context is
+// created after the node is attached to a parent node. If the owner node is
+// reattached to a different parent node, its original blame context gets
+// destroyed and replaced by a new one.
+// Update: Whenever the owner node navigates, it calls UpdateArguments() of
+// its blame context to update its value. The is the only way to update the
+// value of a FrameTreeNodeBlameContext.
+// Deletion: A FrameTreeNodeBlameContext is deleted when its owner node is
+// deleted or reattached to a different parent node.
+
+class FrameTreeNodeBlameContext : public base::trace_event::BlameContext {
+ public:
+  FrameTreeNodeBlameContext(FrameTreeNode* node);
+  ~FrameTreeNodeBlameContext() override;
+  void UpdateArguments();
+
+ private:
+  void AsValueInto(base::trace_event::TracedValue* value) override;
+
+  // Buffered information of the owner node, maintained by UpdateArguments().
+  int process_id_;
+  int routing_id_;
+  GURL url_;
+
+  FrameTreeNode* const owner_;
+
+  DISALLOW_COPY_AND_ASSIGN(FrameTreeNodeBlameContext);
+};
+
+}  // content
+
+#endif  // CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_NODE_BLAME_CONTEXT_H