content: Cleanup IOSurface/SurfaceTexture destruction code.

content/common/gpu/gpu_memory_buffer_factory_surface_texture.cc

 // 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.
 
 #include "content/common/gpu/gpu_memory_buffer_factory_surface_texture.h"
 
 #include "content/common/android/surface_texture_manager.h"
 #include "ui/gl/android/surface_texture.h"
 #include "ui/gl/gl_image_surface_texture.h"
 
@@ skipping 67 matching lines @@
   return handle;
 }
 
 void GpuMemoryBufferFactorySurfaceTexture::DestroyGpuMemoryBuffer(
     gfx::GpuMemoryBufferId id,
     int client_id) {
   {
     base::AutoLock lock(surface_textures_lock_);
 
     SurfaceTextureMapKey key(id, client_id);
-    SurfaceTextureMap::iterator it = surface_textures_.find(key);
-    if (it != surface_textures_.end())
-      surface_textures_.erase(it);
+    DCHECK(surface_textures_.find(key) != surface_textures_.end());
+    surface_textures_.erase(key);
   }
 
   SurfaceTextureManager::GetInstance()->UnregisterSurfaceTexture(id, client_id);
 }
 
 gpu::ImageFactory* GpuMemoryBufferFactorySurfaceTexture::AsImageFactory() {
   return this;
 }
 
 scoped_refptr<gfx::GLImage>
@@ skipping 14 matching lines @@
 
   scoped_refptr<gfx::GLImageSurfaceTexture> image(
       new gfx::GLImageSurfaceTexture(size));
   if (!image->Initialize(it->second.get()))
     return scoped_refptr<gfx::GLImage>();
 
   return image;
 }
 
 }  // namespace content