cc: Leave using_image capability as false when using software.

The value of this currently doesn't matter when using software.

BUG=418553
R=piman@chromium.org

Review URL: https://codereview.chromium.org/615953002

Cr-Commit-Position: refs/heads/master@{#297434}

cc/output/delegating_renderer.cc

@@ -45,7 +45,6 @@ DelegatingRenderer::DelegatingRenderer(RendererClient* client,
 
   if (!output_surface_->context_provider()) {
     capabilities_.using_shared_memory_resources = true;
-    capabilities_.using_image = true;
   } else {
     const ContextProvider::Capabilities& caps =
         output_surface_->context_provider()->ContextCapabilities();