[Rounded Display] Remove code for creating non-overlay gutters.

Currently viz only expects texture generated from overlay gutters as
viz will use the same textures for both overlays and compositing scenario.

This CL, removes the code related to creating non-overlay gutters and updates the unittests accordingly.

Bug: 1262970
Test: Covered by unittests.
Change-Id: I2d86f4d28b55d2a0bf2bff07ae1ac8614642d8ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4438932
Commit-Queue: Zoraiz Naeem <zoraiznaeem@chromium.org>
Reviewed-by: Sean Kau <skau@chromium.org>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1133761}

diff --git a/ash/rounded_display/rounded_display_provider_unittest.cc b/ash/rounded_display/rounded_display_provider_unittest.cc
index efab93a..ebafbe3 100644
--- a/ash/rounded_display/rounded_display_provider_unittest.cc
+++ b/ash/rounded_display/rounded_display_provider_unittest.cc

@@ -94,9 +94,9 @@
   RoundedDisplayProviderTestApi test_api(provider_.get());
   const gfx::RoundedCornersF radii = CreateHorizontallyUniformRadii(10, 12);
 
-  // We expect 4 non-overlays and 2 overlay gutters to be created.
+  // We expect 2 overlay gutters to be created.
   provider_->Init(radii, kDefaultTestStrategy);
-  EXPECT_EQ(test_api.GetGutters().size(), 6u);
+  EXPECT_EQ(test_api.GetGutters().size(), 2u);
 }
 
 TEST_F(RoundedDisplayProviderTest,
@@ -108,7 +108,7 @@
 
   const auto& gutters = test_api.GetGutters();
 
-  EXPECT_EQ(gutters.size(), 6u);
+  EXPECT_EQ(gutters.size(), 2u);
 
   // Check that we have two overlay gutters that in the scanout direction.
   EXPECT_THAT(gutters, testing::Contains(GutterWithMatchingCorners(
@@ -128,7 +128,7 @@
 
   const auto& gutters = test_api.GetGutters();
 
-  EXPECT_EQ(gutters.size(), 6u);
+  EXPECT_EQ(gutters.size(), 2u);
 
   // Check that we have two overlay gutters that in the scanout direction.
   EXPECT_THAT(gutters, testing::Contains(GutterWithMatchingCorners(