Always enable FCM on Windows.

content/browser/gpu/compositor_util_browsertest.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/public/browser/compositor_util.h"
+#include "content/test/content_browser_test.h"
+
+#if defined(OS_WIN)
+#include "base/win/windows_version.h"
+#endif
+
+namespace content {
+
+typedef ContentBrowserTest CompositorUtilTest;
+
+// Test that threaded compositing and FCM are in the expected mode on the bots
+// for all platforms.
+IN_PROC_BROWSER_TEST_F(CompositorUtilTest, CompositingModeAsExpected) {

[gab, 2013/08/06 18:47:07]

Maybe this can be a unit test rather than a browser test; wasn't sure whether
that would be sufficient to make sure the blacklist is loaded, etc. so that
IsForceCompositingModeEnabled() and IsThreadedCompositingEnabled() actually
return the same thing here that they will return in full browser tests.

It felt safer to just make this a browser test to make sure we never end up in a
case where something is not applied for this test (and it thus passes) when the
reality is not the same...

+  enum CompositingMode {
+    DISABLED,
+    ENABLED,
+    THREADED,
+  } expected_mode = DISABLED;
+#if defined(OS_CHROMEOS)
+  expected_mode = THREADED;
+#elif defined(OS_WIN)
+#if defined(USE_AURA)
+  // WinAura always uses threaded compositing.
+  expected_mode = THREADED;
+#else  // defined(USE_AURA)
+  if (base::win::GetVersion() >= base::win::VERSION_VISTA)

[gab, 2013/08/09 14:17:03]

Actually this won't work because the blacklist is disabled on the bots, right?

Talking with wiltzius@ that seemed to be for a legacy reason since we wanted to
blacklist VM GPUs, but not our VMs' GPUs? Now that we have real GPUs on bots (is
that right?) we should be ok with using the blacklist on the bots and then
having this test to make sure that only the bots we expect (XP bots) are
actually blacklisted.

Does that make sense?

[gab, 2013/08/13 21:05:24]

So, should we change the bots to use the blacklist? And have a test (written in
this CL) to make sure the bots use the config we expect them to?

If not, blacklisting XP via the blacklist will not be sufficient to prevent FCM
on the XP bots... and we will need to otherwise hardcode this hard restriction
in code...

+    expected_mode = ENABLED;
+#endif  // defined(USE_AURA)
+#endif
+
+  EXPECT_EQ(expected_mode == ENABLED || expected_mode == THREADED,
+            IsForceCompositingModeEnabled());
+  EXPECT_EQ(expected_mode == THREADED, IsThreadedCompositingEnabled());
+}
+
+}