From 4f74031f0f635e5ffdf4bf54bb614ed738d85bd9 Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@mozilla.com>
Date: Thu, 16 Jul 2015 14:45:06 -0700
Subject: [PATCH] Fix regression where WARP could be used as a fallback on
 Windows 7. (bug 1179051 part 2.1, r=jrmuizel)

--HG--
extra : rebase_source : 0e7932489d2a91d4535047f5d9c59cee323a52cf
---
 gfx/thebes/gfxWindowsPlatform.cpp | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/gfx/thebes/gfxWindowsPlatform.cpp b/gfx/thebes/gfxWindowsPlatform.cpp
index 916ffe23f107..ed5c0e8833b3 100755
--- a/gfx/thebes/gfxWindowsPlatform.cpp
+++ b/gfx/thebes/gfxWindowsPlatform.cpp
@@ -1914,12 +1914,6 @@ gfxWindowsPlatform::CheckD3D11Support() -> D3D11Status
         if (gfxPrefs::LayersD3D11DisableWARP() || GetModuleHandleA("nvdxgiwrap.dll")) {
           return D3D11Status::Blocked;
         }
-
-        if (!IsWin8OrLater()) {
-          // We do not use WARP on Windows 7 or earlier.
-          return D3D11Status::Blocked;
-        }
-
         return D3D11Status::TryWARP;
       }
     }
@@ -1978,10 +1972,6 @@ gfxWindowsPlatform::AttemptD3D11DeviceCreation(const nsTArray<D3D_FEATURE_LEVEL>
 bool
 gfxWindowsPlatform::AttemptWARPDeviceCreation(const nsTArray<D3D_FEATURE_LEVEL>& aFeatureLevels)
 {
-  if (gfxPrefs::LayersD3D11DisableWARP()) {
-    return false;
-  }
-
   MOZ_ASSERT(!mD3D11Device);
 
   ScopedGfxFeatureReporter reporterWARP("D3D11-WARP", gfxPrefs::LayersD3D11ForceWARP());
@@ -2102,11 +2092,16 @@ gfxWindowsPlatform::InitD3D11Devices()
     }
   }
 
-  if (status == D3D11Status::TryWARP || status == D3D11Status::ForceWARP) {
-    if (!AttemptWARPDeviceCreation(featureLevels)) {
-      // Nothing more we can do.
-      return;
-    }
+  if (IsWin8OrLater() &&
+      !gfxPrefs::LayersD3D11DisableWARP() &&
+      (status == D3D11Status::TryWARP || status == D3D11Status::ForceWARP))
+  {
+    AttemptWARPDeviceCreation(featureLevels);
+  }
+
+  if (!mD3D11Device) {
+    // We could not get a D3D11 compositor, and there's nothing more we can try.
+    return;
   }
 
   if (!mD3D11Device) {