Vulkan: Fix issue in DynamicBuffer

- We weren't keeping track of mSize correctly, causing some very
specific index buffer bindings to fail. The size returned when allocating
the buffer can be a bit different than the size requested, and that extra
space between mSize and the allocated size was not meant to be used,
causing errors in the validation layers.

Bug: angleproject:2580
Change-Id: I47eb7b8de6f4f657de14385b77ba6a459add599b
Reviewed-on: https://chromium-review.googlesource.com/1118607
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Luc Ferron <lucferron@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/ProgramVk.cpp b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
index 23fd105..8b9a1cb 100644
--- a/src/libANGLE/renderer/vulkan/ProgramVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
@@ -422,9 +422,8 @@
             // Assume host visible/coherent memory available.
             VkMemoryPropertyFlags flags =
                 (VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT | VK_MEMORY_PROPERTY_HOST_COHERENT_BIT);
-            size_t requiredSize = 0;
             ANGLE_TRY(AllocateBufferMemory(renderer, flags, &mEmptyUniformBlockStorage.buffer,
-                                           &mEmptyUniformBlockStorage.memory, &requiredSize));
+                                           &mEmptyUniformBlockStorage.memory));
         }
 
         // Ensure the descriptor set range includes the uniform buffers at position 0.