WebXR : On desktop GL make sure to use MSAA rather than CMAA when possible.

If the GPU works with MSAA we should use it. However the current code
will always fallback to CMAA on desktop GL because GL_EXT_multisampled_render_to_texture
is only available on ES profile.

While CMAA could be used by other GPUs than Intel, currently Chromium only
provides support for CMAA on Intel GPUs. This patch aligns with the behavior
of DrawingBuffer which is used to render the WebGL content.

Bug: 990923

Change-Id: Ie3a94a68a685fa0b34d573d48f6d4853d553be64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730624Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Alexis Menard <alexis.menard@intel.com>
Auto-Submit: Alexis Menard <alexis.menard@intel.com>
Cr-Commit-Position: refs/heads/master@{#684123}

third_party/blink/renderer/platform/graphics/gpu/xr_webgl_drawing_buffer.cc

@@ -8,6 +8,7 @@
 #include "gpu/GLES2/gl2extchromium.h"
 #include "gpu/command_buffer/client/shared_image_interface.h"
 #include "gpu/command_buffer/common/shared_image_usage.h"
+#include "gpu/config/gpu_driver_bug_workaround_type.h"
 #include "third_party/blink/renderer/platform/graphics/accelerated_static_bitmap_image.h"
 #include "third_party/blink/renderer/platform/graphics/gpu/drawing_buffer.h"
 #include "third_party/blink/renderer/platform/graphics/gpu/extensions_3d_util.h"
@@ -213,7 +214,10 @@ bool XRWebGLDrawingBuffer::Initialize(const IntSize& size,
             "GL_EXT_multisampled_render_to_texture")) {
       anti_aliasing_mode_ = kMSAAImplicitResolve;
     } else if (extensions_util->SupportsExtension(
-                   "GL_CHROMIUM_screen_space_antialiasing")) {
+                   "GL_CHROMIUM_screen_space_antialiasing") &&
+               drawing_buffer_->ContextProvider()
+                   ->GetGpuFeatureInfo()
+                   .IsWorkaroundEnabled(gpu::USE_FRAMEBUFFER_CMAA)) {
       anti_aliasing_mode_ = kScreenSpaceAntialiasing;
     }
   }