No-op incomplete framebuffer invalidation.

src/libANGLE/Context.cpp

@@ -4068,17 +4068,17 @@ void Context::invalidateFramebuffer(GLenum target,
                                     GLsizei numAttachments,
                                     const GLenum *attachments)
 {
-    // Only sync the FBO
-    ANGLE_CONTEXT_TRY(mState.syncDirtyObject(this, target));
-
     Framebuffer *framebuffer = mState.getTargetFramebuffer(target);
     ASSERT(framebuffer);
 
+    // No-op incomplete FBOs.
     if (!framebuffer->isComplete(this))
     {
         return;
     }
 
+    // Only sync the FBO
+    ANGLE_CONTEXT_TRY(mState.syncDirtyObject(this, target));
     ANGLE_CONTEXT_TRY(framebuffer->invalidate(this, numAttachments, attachments));
 }
 

src/tests/gl_tests/FramebufferTest.cpp

@@ -368,9 +368,6 @@ class FramebufferTest_ES3 : public ANGLETest
 // Covers invalidating an incomplete framebuffer. This should be a no-op, but should not error.
 TEST_P(FramebufferTest_ES3, InvalidateIncomplete)
 {
-    // TODO: anglebug.com/3971
-    ANGLE_SKIP_TEST_IF(IsVulkan());
-
     GLFramebuffer framebuffer;
     GLRenderbuffer renderbuffer;