Lots of little cleanup improvements to Vulkan

src/gpu/vk/GrVkGpuCommandBuffer.cpp

Index: src/gpu/vk/GrVkGpuCommandBuffer.cpp
diff --git a/src/gpu/vk/GrVkGpuCommandBuffer.cpp b/src/gpu/vk/GrVkGpuCommandBuffer.cpp
index e3c7cb77cc2692fd50464d93b14a358b4253330f..63fddc1459cc14e4c92d3f7a3f63c7bfc78de59e 100644
--- a/src/gpu/vk/GrVkGpuCommandBuffer.cpp
+++ b/src/gpu/vk/GrVkGpuCommandBuffer.cpp
@@ -57,7 +57,8 @@ GrVkGpuCommandBuffer::GrVkGpuCommandBuffer(GrVkGpu* gpu,
                                            const LoadAndStoreInfo& stencilInfo)
     : fGpu(gpu)
     , fRenderTarget(target)
-    , fIsEmpty(true) {
+    , fIsEmpty(true)
+    , fHasClearStart(false) {
     VkAttachmentLoadOp vkLoadOp;
     VkAttachmentStoreOp vkStoreOp;
 
@@ -101,6 +102,12 @@ void GrVkGpuCommandBuffer::end() {
 }
 
 void GrVkGpuCommandBuffer::onSubmit(const SkIRect& bounds) {
+    if (fIsEmpty && !fHasClearStart) {

[egdaniel, 2016/09/12 20:40:09]

If we grab a texture to which we immediately want to copy to (like dst copy),
grabbing the texture will be a discard batch in, but then when won't actually do
any real work besides a discard. So this allows us to just skip these commands.

+        // We have sumbitted now actual draw commands the the command buffer and we are not using

[Brian Osman, 2016/09/12 20:45:05]

s/now/no/ ?
s/the the/to the/ ?

[jvanverth1, 2016/09/12 20:48:23]

submitted no actual draw commands to the

[egdaniel, 2016/09/12 21:14:32]

Done.

+        // the render pass to do a clear so there is no need to submit anything.
+        return;
+    }
+
     // 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()