Always call DescheduleUntilFinished for WebGL on macOS.

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 6db0e4487e5edda70baf771c684b127dde2608ff..70038e466e192d745d6fceed86222752a0549a85 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -304,8 +304,9 @@ bool DrawingBuffer::prepareMailbox(WebExternalTextureMailbox* outMailbox, WebExt
 
     m_gl->ProduceTextureDirectCHROMIUM(frontColorBufferMailbox->textureInfo.textureId, frontColorBufferMailbox->textureInfo.parameters.target, frontColorBufferMailbox->mailbox.name);
     const GLuint64 fenceSync = m_gl->InsertFenceSyncCHROMIUM();
-    if (RuntimeEnabledFeatures::webGLImageChromiumEnabled())
-        m_gl->DescheduleUntilFinishedCHROMIUM();
+#if OS(MACOSX)
+    m_gl->DescheduleUntilFinishedCHROMIUM();
+#endif
     m_gl->Flush();
     m_gl->GenSyncTokenCHROMIUM(fenceSync, frontColorBufferMailbox->mailbox.syncToken);
     frontColorBufferMailbox->mailbox.validSyncToken = true;