Workaround bogus MscRate reported by some XWayland drivers.

include/platform/FeaturesGL.h

@@ -469,6 +469,12 @@ struct FeaturesGL : FeatureSetBase
         "emulate_pack_skip_rows_and_pack_skip_pixels", FeatureCategory::OpenGLWorkarounds,
         "GL_PACK_SKIP_ROWS and GL_PACK_SKIP_PIXELS are ignored in Apple's OpenGL driver.", &members,
         "https://anglebug.com/4849"};
+
+    // Some drivers return bogus/1hz values for GetMscRate, which we may want to clamp
+    Feature clampMscRate = {
+        "clamp_msc_rate", FeatureCategory::OpenGLWorkarounds,
+        "Some drivers return bogus values for GetMscRate, so we clamp it to 30Hz", &members,
+        "https://crbug.com/1042393"};
 };
 
 inline FeaturesGL::FeaturesGL()  = default;

src/libANGLE/renderer/driver_utils.cpp

@@ -11,6 +11,7 @@
 #include "libANGLE/renderer/driver_utils.h"
 
 #include "common/platform.h"
+#include "common/system_utils.h"
 
 #if defined(ANGLE_PLATFORM_ANDROID)
 #    include <sys/system_properties.h>
@@ -252,4 +253,33 @@ OSVersion GetLinuxOSVersion()
     return OSVersion(0, 0, 0);
 }
 
+// There are multiple environment variables that may or may not be set during Wayland
+// sessions, including WAYLAND_DISPLAY, XDG_SESSION_TYPE, and DESKTOP_SESSION
+bool IsWayland()
+{
+    static bool checked   = false;
+    static bool isWayland = false;
+    if (!checked)
+    {
+        if (IsLinux())
+        {
+            if (!angle::GetEnvironmentVar("WAYLAND_DISPLAY").empty())
+            {
+                isWayland = true;
+            }
+            else if (angle::GetEnvironmentVar("XDG_SESSION_TYPE") == "wayland")
+            {
+                isWayland = true;
+            }
+            else if (angle::GetEnvironmentVar("DESKTOP_SESSION").find("wayland") !=
+                     std::string::npos)
+            {
+                isWayland = true;
+            }
+        }
+        checked = true;
+    }
+    return isWayland;
+}
+
 }  // namespace rx

src/libANGLE/renderer/driver_utils.h

@@ -164,6 +164,8 @@ inline bool IsFuchsia()
 #endif
 }
 
+bool IsWayland();
+
 struct OSVersion
 {
     OSVersion();

src/libANGLE/renderer/gl/glx/DisplayGLX.h

@@ -15,6 +15,7 @@
 
 #include "common/Optional.h"
 #include "libANGLE/renderer/gl/DisplayGL.h"
+#include "libANGLE/renderer/gl/RendererGL.h"
 #include "libANGLE/renderer/gl/glx/FunctionsGLX.h"
 
 namespace rx
@@ -97,6 +98,8 @@ class DisplayGLX : public DisplayGL
 
     void populateFeatureList(angle::FeatureList *features) override;
 
+    RendererGL *getRenderer() const { return mRenderer.get(); }
+
   private:
     egl::Error initializeContext(glx::FBConfig config,
                                  const egl::AttributeMap &eglAttributes,

src/libANGLE/renderer/gl/glx/WindowSurfaceGLX.cpp

@@ -262,6 +262,15 @@ egl::Error WindowSurfaceGLX::getMscRate(EGLint *numerator, EGLint *denominator)
     {
         return egl::EglBadSurface() << "glXGetMscRateOML failed.";
     }
+    if (mGLXDisplay->getRenderer()->getFeatures().clampMscRate.enabled)
+    {
+        // Clamp any refresh rate under 2Hz to 30Hz
+        if (*numerator < *denominator * 2)
+        {
+            *numerator   = 30;
+            *denominator = 1;
+        }
+    }
     return egl::NoError();
 }
 

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -1796,6 +1796,12 @@ void InitializeFeatures(const FunctionsGL *functions, angle::FeaturesGL *feature
     // workaround's being restricted to existing desktop GPUs.
     ANGLE_FEATURE_CONDITION(features, emulatePackSkipRowsAndPackSkipPixels,
                             IsApple() && (isAMD || isIntel || isNvidia));
+
+    // http://crbug.com/1042393
+    // XWayland defaults to a 1hz refresh rate when the "surface is not visible", which sometimes
+    // causes issues in Chrome. To get around this, default to a 30Hz refresh rate if we see bogus
+    // from the driver.
+    ANGLE_FEATURE_CONDITION(features, clampMscRate, IsLinux() && IsWayland());
 }
 
 void InitializeFrontendFeatures(const FunctionsGL *functions, angle::FrontendFeatures *features)