Vulkan: Fix bugs in glGenerateMipmaps.

We had two separate minor bugs. 1) missing a flush of the image data
and 2) missing an initial barrier to set the image to TRANSFER_DST.

Bug: angleproject:2652
Bug: angleproject:2653
Change-Id: I485aafc5c9055b5efb101cb2bc3ebab0588d2639
Reviewed-on: https://chromium-review.googlesource.com/1249564
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>

src/libANGLE/renderer/vulkan/TextureVk.cpp

@@ -809,11 +809,17 @@ angle::Result TextureVk::copyImageDataToBuffer(ContextVk *contextVk,
 
 angle::Result TextureVk::generateMipmapWithBlit(ContextVk *contextVk)
 {
+    ANGLE_TRY(ensureImageInitialized(contextVk));
+
     uint32_t imageLayerCount           = GetImageLayerCount(mState.getType());
     const gl::Extents baseLevelExtents = mImage.getExtents();
     vk::CommandBuffer *commandBuffer   = nullptr;
     ANGLE_TRY(getCommandBufferForWrite(contextVk, &commandBuffer));
 
+    mImage.changeLayoutWithStages(VK_IMAGE_ASPECT_COLOR_BIT, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
+                                  VK_PIPELINE_STAGE_ALL_COMMANDS_BIT,
+                                  VK_PIPELINE_STAGE_ALL_COMMANDS_BIT, commandBuffer);
+
     // We are able to use blitImage since the image format we are using supports it. This
     // is a faster way we can generate the mips.
     int32_t mipWidth  = baseLevelExtents.width;

src/tests/gl_tests/StateChangeTest.cpp

@@ -601,10 +601,6 @@ TEST_P(StateChangeRenderTest, RecreateRenderbuffer)
 // Test that recreating a texture with GenerateMipmaps signals the FBO is dirty.
 TEST_P(StateChangeRenderTest, GenerateMipmap)
 {
-    // TODO(lucferron): Diagnose and fix
-    // http://anglebug.com/2652
-    ANGLE_SKIP_TEST_IF(IsVulkan());
-
     glBindFramebuffer(GL_FRAMEBUFFER, mFramebuffer);
 
     glBindTexture(GL_TEXTURE_2D, mTextures[0]);

src/tests/gl_tests/TextureTest.cpp

@@ -1328,10 +1328,6 @@ TEST_P(SamplerArrayAsFunctionParameterTest, SamplerArrayAsFunctionParameter)
 // Copy of a test in conformance/textures/texture-mips, to test generate mipmaps
 TEST_P(Texture2DTestWithDrawScale, MipmapsTwice)
 {
-    // TODO(lucferron): Diagnose and fix
-    // http://anglebug.com/2653
-    ANGLE_SKIP_TEST_IF(IsVulkan());
-
     int px = getWindowWidth() / 2;
     int py = getWindowHeight() / 2;