Enable Vulkan validation layers on Fuchsia in debug mode. (flutter/engine#3663)

Disable info debug messages from the layers to cut down log spam.

engine/src/flutter/vulkan/vulkan_debug_report.cc

@@ -224,10 +224,13 @@ VulkanDebugReport::VulkanDebugReport(
     return;
   }
 
+  VkDebugReportFlagsEXT flags = kVulkanErrorFlags;
+  if (ValidationLayerInfoMessagesEnabled())
+    flags |= kVulkanInfoFlags;
   const VkDebugReportCallbackCreateInfoEXT create_info = {
       .sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CREATE_INFO_EXT,
       .pNext = nullptr,
-      .flags = kVulkanErrorFlags | kVulkanInfoFlags,
+      .flags = flags,
       .pfnCallback = &vulkan::OnVulkanDebugReportCallback,
       .pUserData = nullptr,
   };

engine/src/flutter/vulkan/vulkan_utilities.cc

@@ -10,10 +10,6 @@
 namespace vulkan {
 
 bool IsDebuggingEnabled() {
-#if OS_FUCHSIA
-  return false;
-#endif
-
 #ifndef NDEBUG
   return true;
 #else
@@ -21,6 +17,12 @@ bool IsDebuggingEnabled() {
 #endif
 }
 
+// Whether to show Vulkan validation layer info messages in addition
+// to the error messages.
+bool ValidationLayerInfoMessagesEnabled() {
+  return false;
+}
+
 static std::vector<std::string> InstanceOrDeviceLayersToEnable(
     const VulkanProcTable& vk,
     VkPhysicalDevice physical_device) {

engine/src/flutter/vulkan/vulkan_utilities.h

@@ -15,6 +15,7 @@
 namespace vulkan {
 
 bool IsDebuggingEnabled();
+bool ValidationLayerInfoMessagesEnabled();
 
 std::vector<std::string> InstanceLayersToEnable(const VulkanProcTable& vk);