Fixed compilation issue on clang 6.x

Bug:dawn:235
Change-Id: If96dbb9f70ee95a93fc1f14a9741903c3fd32b66
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/11942
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
diff --git a/src/dawn_native/vulkan/TextureVk.cpp b/src/dawn_native/vulkan/TextureVk.cpp
index fc412a9..2a26269 100644
--- a/src/dawn_native/vulkan/TextureVk.cpp
+++ b/src/dawn_native/vulkan/TextureVk.cpp
@@ -670,8 +670,9 @@
                                                      VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
                                                      clearDepthStencilValue, 1, &range);
             } else {
+                float fClearColor = static_cast<float>(clearColor);
                 VkClearColorValue clearColorValue = {
-                    {clearColor, clearColor, clearColor, clearColor}};
+                    {fClearColor, fClearColor, fClearColor, fClearColor}};
                 device->fn.CmdClearColorImage(recordingContext->commandBuffer, GetHandle(),
                                               VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
                                               &clearColorValue, 1, &range);