Use a pseudo-extension CHROMIUM_framebuffer_mixed_samples

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index 43c33d1770d54230abfbbf4caf1282565508276f..a7e957cf4d1d1fb60c4efe0feb7515ba5d835555 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -320,7 +320,8 @@ void GrGLCaps::init(const GrContextOptions& contextOptions,
     // We need dual source blending and the ability to disable multisample in order to support mixed
     // samples in every corner case.
     if (fMultisampleDisableSupport && glslCaps->dualSourceBlendingSupport()) {
-        fMixedSamplesSupport = ctxInfo.hasExtension("GL_NV_framebuffer_mixed_samples");
+        fMixedSamplesSupport = ctxInfo.hasExtension("GL_NV_framebuffer_mixed_samples") ||
+                ctxInfo.hasExtension("GL_CHROMIUM_framebuffer_mixed_samples");
         // Workaround NVIDIA bug related to glInvalidateFramebuffer and mixed samples.
         if (fMixedSamplesSupport && kNVIDIA_GrGLDriver == ctxInfo.driver()) {
             fDiscardRenderTargetSupport = false;