[DevTools] Migrate target domain to new generator.

content/browser/devtools/protocol_config.json

 {
     "use_snake_file_names": true,
     "use_title_case_methods": true,
 
     "protocol": {
         "package": "content/browser/devtools/protocol",
         "output": "protocol",
         "namespace": ["content", "protocol"],
         "export_macro": "CONTENT_EXPORT",
         "export_header": "content/common/content_export.h",
@@ skipping 44 matching lines @@
                 "domain": "ServiceWorker"
             },
             {
                 "domain": "Storage"
             },
             {
                 "domain": "SystemInfo",
                 "async": ["getInfo"]
             },
             {
+                "domain": "Target"
+            },
+            {
                 "domain": "Tethering",
                 "async": ["bind", "unbind"]
             },
             {
                 "domain": "Tracing",
                 "async": ["start", "end", "getCategories", "requestMemoryDump"]
             }
         ]
     },
 
     "lib": {
         "package": "content/browser/devtools/protocol",
         "output": "protocol",
         "string_header": "content/browser/devtools/protocol_string.h",
         "export_macro": "CONTENT_EXPORT",
         "export_header": "content/common/content_export.h"
     }
 }