Enable EXT_discard_framebuffer in ANGLE's D3D11 backend.

This doesn't seem to cause the video-related WebGL test failures anymore
that were previously seen.

BUG=497445

Change-Id: I705ae8735823ab7f4b26cf7696cdb746936e4447
Reviewed-on: https://chromium-review.googlesource.com/308001
Tryjob-Request: Kenneth Russell <kbr@chromium.org>
Tested-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/tests/gl_tests/DiscardFramebufferEXTTest.cpp b/src/tests/gl_tests/DiscardFramebufferEXTTest.cpp
index 0543c5a..97b3d76 100644
--- a/src/tests/gl_tests/DiscardFramebufferEXTTest.cpp
+++ b/src/tests/gl_tests/DiscardFramebufferEXTTest.cpp
@@ -30,12 +30,7 @@
 
     if (platform.renderer == EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE)
     {
-        // EXPECT_TRUE(extensionEnabled("EXT_discard_framebuffer"));
-
-        // EXT_discard_framebuffer is disabled in D3D11 ANGLE due to Chromium BUG:497445
-        // Enabling this extension (even as a no-op) causes WebGL video failures in Chromium
-        // Once this bug is fixed, we can reenable the extension.
-        EXPECT_FALSE(extensionEnabled("EXT_discard_framebuffer"));
+        EXPECT_TRUE(extensionEnabled("EXT_discard_framebuffer"));
     }
     else
     {