Vulkan: Implement PACK_STATE dirty bit and remove warning

- also enables all dEQP tests for functional.read_pixels.*

Bug: angleproject:2480

Change-Id: Ib7bcd6b046ff8b0ecf110e70f735036bedf17902
Reviewed-on: https://chromium-review.googlesource.com/1058149
Commit-Queue: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/ContextVk.cpp b/src/libANGLE/renderer/vulkan/ContextVk.cpp
index 25f6edb..5fb95b9 100644
--- a/src/libANGLE/renderer/vulkan/ContextVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ContextVk.cpp
@@ -520,7 +520,8 @@
                 WARN() << "DIRTY_BIT_UNPACK_BUFFER_BINDING unimplemented";
                 break;
             case gl::State::DIRTY_BIT_PACK_STATE:
-                WARN() << "DIRTY_BIT_PACK_STATE unimplemented";
+                // This is a no-op, its only important to use the right pack state when we do
+                // call readPixels later on.
                 break;
             case gl::State::DIRTY_BIT_PACK_BUFFER_BINDING:
                 WARN() << "DIRTY_BIT_PACK_BUFFER_BINDING unimplemented";