Add partial magnifier to ash palette.

The partial magnifier will magnify a small portion of the screen, similar to a spyglass.

TEST=./out/Release/ash_unittests --gtest_filter=PartialMagnificationControllerTest.*
TBR=oshima@chromium.org

BUG=616112

Review-Url: https://codereview.chromium.org/2239553002
Cr-Commit-Position: refs/heads/master@{#414124}
 views::Separator* CreateSeparator(views::Separator::Orientation orientation) {
   const int kSeparatorInset = 10;

  views::Separator* separator =
      new views::Separator(views::Separator::HORIZONTAL);
  separator->SetColor(ash::kBorderDarkColor);
  separator->SetBorder(
      views::Border::CreateEmptyBorder(kSeparatorInset, 0, kSeparatorInset, 0));
  return separator;
}

 views::Separator* CreateSeparator(views::Separator::Orientation orientation) {
   const int kSeparatorInset = 10;

  views::Separator* separator =
      new views::Separator(views::Separator::HORIZONTAL);
  separator->SetColor(ash::kBorderDarkColor);
  separator->SetBorder(
      views::Border::CreateEmptyBorder(kSeparatorInset, 0, kSeparatorInset, 0));
  return separator;
}
