Don't pass buffers to HidConnection::Read because it knows the size.

device/hid/hid_connection_linux.h

 // Copyright (c) 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 DEVICE_HID_HID_CONNECTION_LINUX_H_
 #define DEVICE_HID_HID_CONNECTION_LINUX_H_
 
 #include <queue>
 
 #include "base/files/file.h"
 #include "base/message_loop/message_pump_libevent.h"
 #include "device/hid/hid_connection.h"
 
 namespace device {
 
 class HidConnectionLinux : public HidConnection,
                            public base::MessagePumpLibevent::Watcher {
  public:
   HidConnectionLinux(HidDeviceInfo device_info, std::string dev_node);
 
   // HidConnection implementation.
-  virtual void PlatformRead(scoped_refptr<net::IOBufferWithSize> buffer,
-                            const IOCallback& callback) OVERRIDE;
-  virtual void PlatformWrite(uint8_t report_id,
-                             scoped_refptr<net::IOBufferWithSize> buffer,
-                             const IOCallback& callback) OVERRIDE;
-  virtual void PlatformGetFeatureReport(
-      uint8_t report_id,
-      scoped_refptr<net::IOBufferWithSize> buffer,
-      const IOCallback& callback) OVERRIDE;
+  virtual void PlatformRead(const ReadCallback& callback) OVERRIDE;
+  virtual void PlatformWrite(scoped_refptr<net::IOBuffer> buffer,
+                             size_t size,
+                             const WriteCallback& callback) OVERRIDE;
+  virtual void PlatformGetFeatureReport(uint8_t report_id,
+                                        const ReadCallback& callback) OVERRIDE;
   virtual void PlatformSendFeatureReport(
-      uint8_t report_id,
-      scoped_refptr<net::IOBufferWithSize> buffer,
-      const IOCallback& callback) OVERRIDE;
+      scoped_refptr<net::IOBuffer> buffer,
+      size_t size,
+      const WriteCallback& callback) OVERRIDE;
 
   // base::MessagePumpLibevent::Watcher implementation.
   virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
   virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
 
  private:
   friend class base::RefCountedThreadSafe<HidConnectionLinux>;
   virtual ~HidConnectionLinux();
 
   void Disconnect();
 
   void Flush();
-  void ProcessInputReport(scoped_refptr<net::IOBufferWithSize> buffer);
+  void ProcessInputReport(scoped_refptr<net::IOBuffer> buffer, size_t size);
   void ProcessReadQueue();
 
   base::File device_file_;
   base::MessagePumpLibevent::FileDescriptorWatcher device_file_watcher_;
 
   std::queue<PendingHidReport> pending_reports_;
   std::queue<PendingHidRead> pending_reads_;
 
   DISALLOW_COPY_AND_ASSIGN(HidConnectionLinux);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_HID_HID_CONNECTION_LINUX_H_