Disable ignore discard optimization in Vulkan

src/gpu/vk/GrVkGpuCommandBuffer.cpp

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "GrVkGpuCommandBuffer.h"
 
 #include "GrFixedClip.h"
@@ skipping 84 matching lines @@
     fRenderPass->unref(fGpu);
 }
 
 GrGpu* GrVkGpuCommandBuffer::gpu() { return fGpu; }
 
 void GrVkGpuCommandBuffer::end() {
     fCommandBuffer->end(fGpu);
 }
 
 void GrVkGpuCommandBuffer::onSubmit(const SkIRect& bounds) {
+    // TODO: We can't add this optimization yet since many things create a scratch texture which
+    // adds the discard immediately, but then don't draw to it right away. This causes the discard
+    // to be ignored and we get yelled at for loading uninitialized data. However, once MDP lands,
+    // the discard will get reordered with the rest of the draw commands and we can re-enable this.
+#if 0
     if (fIsEmpty && !fStartsWithClear) {
         // We have sumbitted no actual draw commands to the command buffer and we are not using
         // the render pass to do a clear so there is no need to submit anything.
         return;
     }
+#endif
 
     // Change layout of our render target so it can be used as the color attachment. Currently
     // we don't attach the resolve to the framebuffer so no need to change its layout.
     GrVkImage* targetImage = fRenderTarget->msaaImage() ? fRenderTarget->msaaImage()
                                                         : fRenderTarget;
     targetImage->setImageLayout(fGpu,
                                 VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL,
                                 VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT,
                                 VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT,
                                 false);
@@ skipping 325 matching lines @@
             fGpu->stats()->incNumDraws();
         } while ((nonIdxMesh = iter.next()));
     }
 
     // Technically we don't have to call this here (since there is a safety check in
     // pipelineState:setData but this will allow for quicker freeing of resources if the
     // pipelineState sits in a cache for a while.
     pipelineState->freeTempResources(fGpu);
 }