Reland "[Fuchsia] Reenable protected mode in WebEngine"

This is a reland of a2c0ced3

Original change's description:
> [Fuchsia] Reenable protected mode in WebEngine
> 
> Bug: 982922, fuchsia:24570
> Change-Id: If9fb495249488c43f97e4451a14f0193911d600f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1804527
> Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
> Commit-Queue: Emircan Uysaler <emircan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#697683}

Bug: 982922, fuchsia:24570
Change-Id: Id4c70e7efbc1ba5c39f08178c5f8c62559838973
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1877193Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Emircan Uysaler <emircan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709338}

fuchsia/engine/context_provider_impl.cc

@@ -257,6 +257,10 @@ void ContextProviderImpl::Create(
                                      switches::kGrContextTypeVulkan);
   }
 
+  if (enable_protected_graphics) {
+    launch_command.AppendSwitch(switches::kEnforceVulkanProtectedMemory);
+  }
+
   if (enable_widevine) {
     launch_command.AppendSwitch(switches::kEnableWidevine);
   }