Refactor UniqueNameHelper to use an adapter pattern for code sharing.

content/renderer/render_frame_impl.h

Index: content/renderer/render_frame_impl.h
diff --git a/content/renderer/render_frame_impl.h b/content/renderer/render_frame_impl.h
index adf66eed6e52bc7655aa02271d5100046cbf6930..2a669da9613c8fa9b0e6680aef886dd63e8a030c 100644
--- a/content/renderer/render_frame_impl.h
+++ b/content/renderer/render_frame_impl.h
@@ -37,6 +37,7 @@
 #include "content/common/frame_message_enums.h"
 #include "content/common/host_zoom.mojom.h"
 #include "content/common/renderer.mojom.h"
+#include "content/common/unique_name_helper.h"
 #include "content/common/url_loader_factory.mojom.h"
 #include "content/public/common/console_message_level.h"
 #include "content/public/common/javascript_dialog_type.h"
@@ -48,7 +49,6 @@
 #include "content/renderer/frame_blame_context.h"
 #include "content/renderer/mojo/blink_interface_provider_impl.h"
 #include "content/renderer/renderer_webcookiejar_impl.h"
-#include "content/renderer/unique_name_helper.h"
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_platform_file.h"
 #include "media/base/routing_token_callback.h"
@@ -1167,6 +1167,28 @@ class CONTENT_EXPORT RenderFrameImpl
   // |frame_| has been invalidated.
   bool is_main_frame_;
 
+  class RenderFrameAdapter : public UniqueNameHelper::FrameAdapter {
+   public:
+    explicit RenderFrameAdapter(RenderFrameImpl* render_frame);
+    ~RenderFrameAdapter() override;
+
+    // FrameAdapter overrides:
+    bool IsMainFrame() const override;
+    bool IsCandidateUnique(const std::string& name) const override;
+    int GetSiblingCount() const override;
+    int GetChildCount() const override;
+    std::vector<base::StringPiece> CollectAncestorNames(
+        BeginPoint begin_point,
+        bool (*should_stop)(base::StringPiece)) const override;
+    std::vector<int> GetFramePosition(BeginPoint begin_point) const override;
+
+   private:
+    blink::WebLocalFrame* GetWebFrame() const;
+
+    RenderFrameImpl* render_frame_;
+  };
+  // TODO(dcheng): This name is not good.
+  RenderFrameAdapter render_frame_adapter_;

[Łukasz Anforowicz, 2017/05/25 16:48:50]

Optional: Have you considered hiding the RenderFrameAdapter class in an
anonymous namespace inside render_frame_impl.cc?  (and changing
RenderFrameAdapter type below into
std::unique_ptr<UniqueNameHelper::FrameAdapter>).

[dcheng, 2017/05/25 18:25:03]

I considered that. While it hides the subclass definition, it introduces an
unnecessary heap indirection. Internal Google style is to avoid using forward
declares just to avoid including a full definition.

One option would be to move it to a separate file, but then I really need to
find a better name =)

[Łukasz Anforowicz, 2017/05/25 18:33:18]

FWIW, the current name is not that bad IMO.  If you want to change it, then
maybe UniqueNameFrameAdapter (since the "Render" part is implied by having the
class nested within RenderFrame)?

[dcheng, 2017/05/25 18:40:41]

Done.

   UniqueNameHelper unique_name_helper_;
 
   // When a frame is detached in response to a message from the browser process,