Don't try to populate maps from dirty resources with no initial contents

* If a buffer has been marked as dirty mid-frame but wasn't dirty at the start
  of the frame then it won't have initial contents. We have to treat it as if it
  wasn't dirty and fall back to using our existing data for it, assuming that is
  a valid way to pre-populate the map's shadow buffer.

renderdoc/driver/d3d11/d3d11_context_wrap.cpp

@@ -7398,15 +7398,13 @@ bool WrappedID3D11DeviceContext::Serialise_Map(SerialiserType &ser, ID3D11Resour
 
       if(MapType != D3D11_MAP_WRITE_DISCARD)
       {
-        if(m_pDevice->GetResourceManager()->IsResourceDirty(Resource))
-        {
-          ID3D11DeviceChild *initial =
-              m_pDevice->GetResourceManager()->GetInitialContents(Resource).resource;
+        ID3D11DeviceChild *initial =
+            m_pDevice->GetResourceManager()->GetInitialContents(Resource).resource;
 
+        if(initial)
+        {
           if(WrappedID3D11Buffer::IsAlloc(pResource))
           {
-            RDCASSERT(initial);
-
             ID3D11Buffer *stage = (ID3D11Buffer *)initial;
 
             D3D11_MAPPED_SUBRESOURCE mapped;

util/test/demos/d3d11/d3d11_resource_lifetimes.cpp

@@ -98,6 +98,21 @@ float4 main(v2f IN) : SV_Target0
       return ret;
     };
 
+    ID3D11BufferPtr dummy = MakeBuffer().Constant().Size(sizeof(Vec4f));
+
+    auto SetupVBuf = [this, dummy]() {
+      ID3D11BufferPtr ret = MakeBuffer().Vertex().Size(sizeof(Vec4f)).Mappable();
+
+      // force the buffer to become dirty
+      ctx->CopyResource(ret, dummy);
+
+      // map the dirty resource
+      D3D11_MAPPED_SUBRESOURCE map = Map(ret, 0, D3D11_MAP_WRITE_NO_OVERWRITE);
+      ctx->Unmap(ret, 0);
+
+      return ret;
+    };
+
     auto TrashBuf = [this](ID3D11BufferPtr &buf) {
       D3D11_MAPPED_SUBRESOURCE map = Map(buf, 0, D3D11_MAP_WRITE_DISCARD);
       memset(map.pData, 0, sizeof(Vec4f));
@@ -177,6 +192,10 @@ float4 main(v2f IN) : SV_Target0
       TrashBuf(cb);
       TrashSRV(srv);
 
+      // create, dirty, and map the dirty buffer mid-frame
+      ID3D11BufferPtr vbtmp = SetupVBuf();
+      TrashBuf(vbtmp);
+
       // set up resources for next frame
       cb = SetupBuf();
       srv = SetupSRV();