Fix integer overflow in software compositor

Ensure that the size mapped from the renderer
process for the software frame is not less than
expected due to integer overflow.

BUG=348332

Review URL: https://codereview.chromium.org/196283018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257417 0039d316-1c4b-4281-b951-d872f2087c98
void SoftwareFrameManager::GetCurrentFrameMailbox(
    cc::TextureMailbox* mailbox,
    scoped_ptr<cc::SingleReleaseCallback>* callback) {
  DCHECK(HasCurrentFrame());
  *mailbox = cc::TextureMailbox(
      current_frame_->shared_memory_.get(), current_frame_->frame_size_pixels_);
  *callback = cc::SingleReleaseCallback::Create(
      base::Bind(ReleaseMailbox, current_frame_));
}

void SoftwareFrameManager::GetCurrentFrameMailbox(
    cc::TextureMailbox* mailbox,
    scoped_ptr<cc::SingleReleaseCallback>* callback) {
  DCHECK(HasCurrentFrame());
  *mailbox = cc::TextureMailbox(
      current_frame_->shared_memory_.get(), current_frame_->frame_size_pixels_);
  *callback = cc::SingleReleaseCallback::Create(
      base::Bind(ReleaseMailbox, current_frame_));
}
