Split infobars.{cc,h} into separate pieces for the different classes defined within, so that each piece is shorter and clearer.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/6250057

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@73235 0039d316-1c4b-4281-b951-d872f2087c98
void InfoBar::Layout() {
  gfx::Size button_ps = close_button_->GetPreferredSize();
  close_button_->SetBounds(width() - kHorizontalPadding - button_ps.width(),
                           OffsetY(this, button_ps), button_ps.width(),
                           button_ps.height());
}

void InfoBar::Layout() {
  gfx::Size button_ps = close_button_->GetPreferredSize();
  close_button_->SetBounds(width() - kHorizontalPadding - button_ps.width(),
                           OffsetY(this, button_ps), button_ps.width(),
                           button_ps.height());
}
