Hook up guest browser plugins to the accessibility tree.

content/browser/frame_host/frame_accessibility.h

+// Copyright 2014 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_ACCESSIBILITY_H_
+#define CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/memory/singleton.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class RenderFrameHostImpl;
+
+// This singleton class maintains the mappings necessary to link child frames

[Charlie Reis, 2014/09/11 21:46:21]

Are there any potential issues with this being a singleton?  For example, could
it mix frames from different Profiles if someone passed in the wrong ID?

(I see that you're checking that nodes belong to the same FrameTree in some
places, which helps.  Not sure if that covers all the cases.)

[dmazzoni, 2014/09/12 07:34:34]

Good idea. The best place to check for this is just before we retrieve a frame,
so I added a check to RenderFrameHostImpl::AccessibilityGetParentFrame and
AccessibilityGetChildFrame that makes sure the browser contexts match. I also
realized that I was checking for the same FrameTree when retrieving a child but
not a parent, so I fixed that. I made them all DCHECKs that return NULL in
release mode so that a compromised renderer can't use this to crash the browser.

I can't think of any issues with this being a singleton as long as we have good
checks like these.

+// and guest frames into a single tree for accessibility. This class is only
+// used if accessibility is enabled.
+class CONTENT_EXPORT FrameAccessibility {
+ public:
+  static FrameAccessibility* GetInstance();
+
+  // Add a mapping between an accessibility node of |parent_frame_host|
+  // and the child frame with the given frame tree node id, in the same
+  // frame tree.
+  void AddChildFrame(RenderFrameHostImpl* parent_frame_host,
+                     int accessibility_node_id,
+                     int64 child_frame_tree_node_id);
+
+  // Add a mapping between an accessibility node of |parent_frame_host|
+  // and the main frame of the guest Webcontents with the given
+  // browser plugin instance id.
+  void AddGuestWebContents(RenderFrameHostImpl* parent_frame_host,
+                           int accessibility_node_id,
+                           int browser_plugin_instance_id);
+
+  // This is called when a RenderFrameHostImpl is deleted, so invalid
+  // mappings can be removed from this data structure.
+  void OnRenderFrameHostDestroyed(RenderFrameHostImpl* render_frame_host);
+
+  // Given a parent RenderFrameHostImpl and an accessibility node id, look up
+  // a child frame or guest frame that was previously associated with this
+  // frame and node id. If a mapping exists, return the resulting frame if
+  // it's valid. If it doesn't resolve to a valid RenderFrameHostImpl,
+  // returns NULL.
+  RenderFrameHostImpl* GetChild(RenderFrameHostImpl* parent_frame_host,
+                                int accessibility_node_id);
+
+  // Given a RenderFrameHostImpl, check the mapping table to see if it's
+  // the child of a node in some other frame. If so, return true and
+  // set the parent frame and accessibility node id in the parent frame,
+  // otherwise return false.
+  bool GetParent(RenderFrameHostImpl* child_frame_host,
+                 RenderFrameHostImpl** out_parent_frame_host,
+                 int* out_accessibility_node_id);
+
+ private:
+  FrameAccessibility();
+  virtual ~FrameAccessibility();
+
+  struct ChildFrameMapping {
+    ChildFrameMapping();
+
+    RenderFrameHostImpl* parent_frame_host;
+    int accessibility_node_id;
+    int64 child_frame_tree_node_id;
+    int browser_plugin_instance_id;
+  };
+
+  std::vector<ChildFrameMapping> mappings_;
+
+  friend struct DefaultSingletonTraits<FrameAccessibility>;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_