Alternative fix for stale MIP maps on texture export/import.

This change assumes imported textures in SkImages have dirty mip levels
and disables regenerating the MIP levels on export (added in
https://skia.googlesource.com/skia/+/930f939c48af1be6005af12bb6f709ca5da9d118).

This is being done temporarily because it is a simpler change to cherry
pick to earlier branches than
https://skia.googlesource.com/skia/+/930f939c48af1be6005af12bb6f709ca5da9d118

Bug: chromium:850617
Change-Id: I7c90da782a0ed9014acd6a54ffdee1a0b34fa00c
Reviewed-on: https://skia-review.googlesource.com/136788
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrDrawingManager.cpp b/src/gpu/GrDrawingManager.cpp
index fcee576..d481632 100644
--- a/src/gpu/GrDrawingManager.cpp
+++ b/src/gpu/GrDrawingManager.cpp
@@ -382,12 +382,16 @@
     if (auto* rt = surface->asRenderTarget()) {
         gpu->resolveRenderTarget(rt);
     }
+#if 0
+    // This is temporarily is disabled. See comment in SkImage_Gpu.cpp,
+    // new_wrapped_texture_common().
     if (auto* tex = surface->asTexture()) {
         if (tex->texturePriv().mipMapped() == GrMipMapped::kYes &&
             tex->texturePriv().mipMapsAreDirty()) {
             gpu->regenerateMipMapLevels(tex);
         }
     }
+#endif
     return result;
 }