Make SharedMemory track the size that was actually mapped

ui/surface/transport_dib.h

 // 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 UI_SURFACE_TRANSPORT_DIB_H_
 #define UI_SURFACE_TRANSPORT_DIB_H_
 
 #include "base/basictypes.h"
 #include "ui/surface/surface_export.h"
 
@@ skipping 187 matching lines @@
   // detached.
   void DecreaseInFlightCounter();
 
   // Deletes this transport DIB and detaches the shared memory once the
   // |inflight_counter_| is zero.
   void Detach();
 #endif
 
  private:
   TransportDIB();
+
+  // Verifies that the dib can hold a canvas of the requested dimensions.
+  bool VerifyCanvasSize(int w, int h);
+
 #if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_ANDROID)
   explicit TransportDIB(base::SharedMemoryHandle dib);
   base::SharedMemory shared_memory_;
   uint32 sequence_num_;
 #elif defined(USE_X11)
   Id key_;  // SysV shared memory id
   void* address_;  // mapped address
   XSharedMemoryId x_shm_;  // X id for the shared segment
   Display* display_;  // connection to the X server
   size_t inflight_counter_;  // How many requests to the X server are in flight
   bool detached_;  // If true, delete the transport DIB when it is idle
 #endif
   size_t size_;  // length, in bytes
 
   DISALLOW_COPY_AND_ASSIGN(TransportDIB);
 };
 
 #endif  // UI_SURFACE_TRANSPORT_DIB_H_