Re-land "Added support for premultiplied alpha mode for composition swapchains"

Change-Id: Ic0c863c3d4936947fc520a5394e38e458659df46
Reviewed-on: https://chromium-review.googlesource.com/298880
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/tests/gl_tests/D3D11InputLayoutCacheTest.cpp b/src/tests/gl_tests/D3D11InputLayoutCacheTest.cpp
index ab1d549..546399c 100644
--- a/src/tests/gl_tests/D3D11InputLayoutCacheTest.cpp
+++ b/src/tests/gl_tests/D3D11InputLayoutCacheTest.cpp
@@ -27,6 +27,7 @@
         setWindowWidth(64);
         setWindowHeight(64);
         setConfigRedBits(8);
+        setConfigAlphaBits(8);
     }
 
     GLuint makeProgramWithAttribCount(unsigned int attribCount)