Vulkan: Expose the unimplemented GL_EXT_occlusion_query_boolean extension.

Chrome needs this extension to be exposed to load the query entry points,
even for emulated query types.

BUG=angleproject:2855

Change-Id: I09dbb45c391df64d67858f9131c45b164947a707
Reviewed-on: https://chromium-review.googlesource.com/1255507
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>

src/libANGLE/renderer/vulkan/vk_caps_utils.cpp

@@ -48,6 +48,9 @@ void GenerateCaps(const VkPhysicalDeviceProperties &physicalDeviceProperties,
     outExtensions->debugMarker     = true;
     outExtensions->robustness      = true;
 
+    // TODO: Not implemented yet but exposed so that Chrome can load the query entry points.  http://anglebug.com/2855
+    outExtensions->occlusionQueryBoolean = true;
+
     // TODO(lucferron): Eventually remove everything above this line in this function as the caps
     // get implemented.
     // https://vulkan.lunarg.com/doc/view/1.0.30.0/linux/vkspec.chunked/ch31s02.html