cc: Remove all usage of GetArea() from production code in cc

cc/resources/texture_mailbox.cc

 // Copyright 2013 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 "cc/resources/texture_mailbox.h"
 
 #include "base/logging.h"
+#include "cc/resources/shared_bitmap.h"
 #include "third_party/khronos/GLES2/gl2.h"
 
 namespace cc {
 
 TextureMailbox::TextureMailbox() : shared_memory_(NULL) {}
 
 TextureMailbox::TextureMailbox(const gpu::MailboxHolder& mailbox_holder)
     : mailbox_holder_(mailbox_holder),
       shared_memory_(NULL),
       allow_overlay_(false) {}
 
 TextureMailbox::TextureMailbox(const gpu::Mailbox& mailbox,
                                uint32 target,
                                uint32 sync_point)
     : mailbox_holder_(mailbox, target, sync_point),
       shared_memory_(NULL),
       allow_overlay_(false) {}
 
 TextureMailbox::TextureMailbox(base::SharedMemory* shared_memory,
                                const gfx::Size& size)
     : shared_memory_(shared_memory),
       shared_memory_size_(size),
       allow_overlay_(false) {
   // If an embedder of cc gives an invalid TextureMailbox, we should crash
-  // safely rather than overflow.
-  CHECK(CheckedSharedMemorySizeInBytes().IsValid());
+  // here to identify the offender.
+  CHECK(SharedBitmap::VerifySizeInBytes(shared_memory_size_));
 }
 
 TextureMailbox::~TextureMailbox() {}
 
 bool TextureMailbox::Equals(const TextureMailbox& other) const {
   if (other.IsTexture()) {
     return IsTexture() && !memcmp(mailbox_holder_.mailbox.name,
                                   other.mailbox_holder_.mailbox.name,
                                   sizeof(mailbox_holder_.mailbox.name));
   } else if (other.IsSharedMemory()) {
     return IsSharedMemory() &&
            shared_memory_->handle() == other.shared_memory_->handle();
   }
 
   DCHECK(!other.IsValid());
   return !IsValid();
 }
 
 size_t TextureMailbox::SharedMemorySizeInBytes() const {
-  size_t bytes_per_pixel = 4;
-  size_t width = shared_memory_size_.width();
-  size_t height = shared_memory_size_.height();
-  return bytes_per_pixel * width * height;
-}
-
-base::CheckedNumeric<size_t> TextureMailbox::CheckedSharedMemorySizeInBytes()
-    const {
-  return base::CheckedNumeric<size_t>(4) *
-         base::CheckedNumeric<size_t>(shared_memory_size_.width()) *
-         base::CheckedNumeric<size_t>(shared_memory_size_.height());
+  // UncheckedSizeInBytes is okay because we VerifySizeInBytes in the
+  // constructor and the field is immutable.
+  return SharedBitmap::UncheckedSizeInBytes(shared_memory_size_);
 }
 
 }  // namespace cc