Attaching an image to many color attachment points is unsupported

gpu/command_buffer/service/framebuffer_manager.cc

Index: gpu/command_buffer/service/framebuffer_manager.cc
diff --git a/gpu/command_buffer/service/framebuffer_manager.cc b/gpu/command_buffer/service/framebuffer_manager.cc
index cec5b104b7ab678b71a164d4da999293e99df8a8..84a77d46e74d5175c74c392eca676f0a5cab0ca0 100644
--- a/gpu/command_buffer/service/framebuffer_manager.cc
+++ b/gpu/command_buffer/service/framebuffer_manager.cc
@@ -89,6 +89,15 @@ class RenderbufferAttachment
     return renderbuffer_.get() == renderbuffer;
   }
 
+  bool IsSameAttachment(const Attachment* attachment) const override {
+    if (attachment->IsRenderbufferAttachment()) {
+      const RenderbufferAttachment* other =
+          reinterpret_cast<const RenderbufferAttachment*>(attachment);
+      return IsRenderbuffer(other->renderbuffer());
+    }
+    return false;
+  }
+
   bool Is3D() const override { return false; }
 
   bool CanRenderTo(const FeatureInfo*) const override { return true; }
@@ -220,6 +229,18 @@ class TextureAttachment
     return texture == texture_ref_.get();
   }
 
+  bool IsSameAttachment(const Attachment* attachment) const override {
+    if (attachment->IsTextureAttachment()) {
+      const TextureAttachment* other =
+          reinterpret_cast<const TextureAttachment*>(attachment);
+      return IsTexture(other->texture()) &&
+          layer_ == other->layer() &&
+          target_ == other->target() &&
+          level_ == other->level();
+    }
+    return false;
+  }
+
   bool IsRenderbuffer(Renderbuffer* /* renderbuffer */) const override {
     return false;
   }
@@ -711,6 +732,19 @@ GLenum Framebuffer::IsPossiblyComplete(const FeatureInfo* feature_info) const {
     if (!attachment->CanRenderTo(feature_info)) {
       return GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT;
     }
+
+    // Attaching an image to more than one color attachment point should return
+    // FRAMEBUFFER_UNSUPPORTED.
+    if (it->first >= GL_COLOR_ATTACHMENT0 &&
+        it->first < GL_COLOR_ATTACHMENT0 + manager_->max_color_attachments_) {
+      for (GLenum i = it->first + 1;
+           i < GL_COLOR_ATTACHMENT0 + manager_->max_color_attachments_; i++) {
+        const Attachment* other = GetAttachment(i);
+        if (other && attachment->IsSameAttachment(other)) {
+          return GL_FRAMEBUFFER_UNSUPPORTED;
+        }
+      }
+    }
   }
 
   // This does not mean the framebuffer is actually complete. It just means our