Fix WebView compositor input handling

content/renderer/gpu/input_handler_manager_client.h

Index: content/renderer/gpu/input_handler_manager_client.h
diff --git a/content/renderer/gpu/input_handler_manager_client.h b/content/renderer/gpu/input_handler_manager_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..ef218bd42313daad166b656fda40abce032cc578
--- /dev/null
+++ b/content/renderer/gpu/input_handler_manager_client.h
@@ -0,0 +1,48 @@
+// Copyright (c) 2012 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_RENDERER_GPU_INPUT_HANDLER_MANAGER_CLIENT_H_
+#define CONTENT_RENDERER_GPU_INPUT_HANDLER_MANAGER_CLIENT_H_
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+
+namespace WebKit {
+class WebInputEvent;
+}
+
+namespace content {
+
+class InputHandlerManagerClient {
+ public:
+  virtual ~InputHandlerManagerClient() {}
+
+  // The Handler allows the client to forward input events in such a way that
+  // callbacks to DidHandleInputEvent or DidNotHandlerInputEvent are made with
+  // the appropriate response.
+  // The Manager guarantees that the supplied |handler| is valid, but only until
+  // the next call to DidBind. The client should only makes calls to |handler|

[joth, 2013/05/31 18:05:08]

ah! DidBind() will be called multiple times, and with a null Handler() in the
going-away case.

I wonder is something more direct like SetBoundHanlder() would be clearer in
this case?

whatever, add a comment below that it will be called multiple times

[jdduke (slow), 2013/05/31 20:48:24]

Yeah, I'm open to changing this.  I had it as SetHandler() for a while. 

Eventually I'd like the Did/DidNotHandle callbacks to go away completely, and we
simply get the handled event disposition from the Handler.

+  // on the compositing thread.
+  typedef base::Callback<void(int /*routing_id*/,
+                              const WebKit::WebInputEvent*)> Handler;
+
+  // Called from the main thread.
+  virtual void DidBind(const Handler& handler) = 0;
+  virtual void DidAddInputHandler(int routing_id) = 0;

[joth, 2013/05/31 18:05:08]

It's be useful to repeat the contract on when and why each of these should be
called (or, link to the class that defines the protocol).

I'd find it handy to have the OnXxxThread called out in the function names, but
that maybe over-verbose for anyone semi-familiar with this code.

[jdduke (slow), 2013/05/31 20:48:24]

Yeah.  I really think these two callback methods should disappear. I have a
patch with such a change; for now they simply retain the method names from
before.

+  virtual void DidRemoveInputHandler(int routing_id) = 0;
+
+  // Called from the compositing thread.
+  virtual void DidHandleInputEvent() = 0;
+  virtual void DidNotHandleInputEvent(bool send_to_widget) = 0;
+
+ protected:
+  InputHandlerManagerClient() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(InputHandlerManagerClient);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_INPUT_HANDLER_MANAGER_CLIENT_H_