Create child window in GPU process for DirectComposition

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 1b515311c15e1cdecfb2d4d63e004688b6ccb9a2..5327dd5c0ed08a7ff4b15cfafebc8b16eb9c98a8 100644
--- a/ui/gl/gl_switches.cc
+++ b/ui/gl/gl_switches.cc
@@ -66,6 +66,9 @@ const char kSwiftShaderPath[]               = "swiftshader-path";
 // context will never be lost in any situations, say, a GPU reset.
 const char kGpuNoContextLost[]              = "gpu-no-context-lost";
 
+// Turns on the use of DirectComposition to draw to the screen.
+const char kUseDirectComposition[] = "use-direct-composition";
+
 // Indicates whether the dual GPU switching is supported or not.
 const char kSupportsDualGpus[]              = "supports-dual-gpus";
 
@@ -103,6 +106,7 @@ const char* kGLSwitchesCopiedFromGpuProcessHost[] = {
   kDisableGLDrawingForTests,
   kOverrideUseGLWithOSMesaForTests,
   kUseANGLE,
+  kUseDirectComposition,
 };
 const int kGLSwitchesCopiedFromGpuProcessHostNumSwitches =
     arraysize(kGLSwitchesCopiedFromGpuProcessHost);