Disable partial swap on windows

ui/gl/gl_surface_egl.cc

Index: ui/gl/gl_surface_egl.cc
diff --git a/ui/gl/gl_surface_egl.cc b/ui/gl/gl_surface_egl.cc
index 3f8923ae895ecc38887237d6bd09f3c9425aa6e1..b03a49a1fa399b80ca9d16c50aeb87bf48eebee2 100644
--- a/ui/gl/gl_surface_egl.cc
+++ b/ui/gl/gl_surface_egl.cc
@@ -295,6 +295,11 @@ bool NativeViewGLSurfaceEGL::Initialize(VSyncProvider* sync_provider) {
                                       &surfaceVal);
   supports_post_sub_buffer_ = (surfaceVal && retVal) == EGL_TRUE;
 
+#if defined(OS_WIN)
+  // Partial swaps may be causing performance issues on Windows.
+  supports_post_sub_buffer_ = false;
+#endif
+
   if (sync_provider)
     vsync_provider_.swap(vsync_provider);
   else if (g_egl_sync_control_supported)