adds WARP support to Chromium, for Metro mode only, on Windows 8

ui/gl/gl_switches.cc

Index: ui/gl/gl_switches.cc
diff --git a/ui/gl/gl_switches.cc b/ui/gl/gl_switches.cc
index 7eaa3d8c464464888071babb3245a5ad38c59734..e5e9f254bf693907b44c467da189eae9d5660b2c 100644
--- a/ui/gl/gl_switches.cc
+++ b/ui/gl/gl_switches.cc
@@ -56,6 +56,9 @@ const char kTestGLLib[]                     = "test-gl-lib";
 // Use hardware gpu, if available, for tests.
 const char kUseGpuInTests[] = "use-gpu-in-tests";
 
+// On Windows only: use the WARP software rasterizer in the GPU process.
+const char kUseWarp[] = "use-warp";
+
 // Disables GL drawing operations which produce pixel output. With this
 // the GL output will not be correct but tests will run faster.
 const char kDisableGLDrawingForTests[] = "disable-gl-drawing-for-tests";
@@ -75,6 +78,7 @@ const char* kGLSwitchesCopiedFromGpuProcessHost[] = {
   kGpuNoContextLost,
   kDisableGLDrawingForTests,
   kOverrideUseGLWithOSMesaForTests,
+  kUseWarp
 };
 const int kGLSwitchesCopiedFromGpuProcessHostNumSwitches =
     arraysize(kGLSwitchesCopiedFromGpuProcessHost);