Disable RenderPassTest.TwoRenderPassesInOneCommandBuffer on OpenGL and Metal

This test is flaky on Metal and consistently failing on OpenGL.

TBR=cwallez@chromium.org,kainino@chromium.org
Bug: chromium:950768
Change-Id: I0e62b87053009182afef39e5ef2459b30a866418
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/6500
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>

src/tests/end2end/RenderPassTests.cpp

@@ -72,6 +72,11 @@ protected:
 
 // Test using two different render passes in one commandBuffer works correctly.
 TEST_P(RenderPassTest, TwoRenderPassesInOneCommandBuffer) {
+    if (IsOpenGL() || IsMetal()) {
+      // crbug.com/950768
+      // This test is consistently failing on OpenGL and flaky on Metal.
+      return;
+    }
     constexpr RGBA8 kRed(255, 0, 0, 255);
     constexpr RGBA8 kGreen(0, 255, 0, 255);