[devtools] Add DOMSnapshot domain for dom+layout+style snapshots.

third_party/WebKit/Source/core/inspector/inspector_protocol_config.json

 {
     "protocol": {
         "path": "browser_protocol.json",
         "package": "core/inspector/protocol",
         "output": "inspector/protocol",
         "namespace": ["blink", "protocol"],
         "export_macro": "CORE_EXPORT",
         "export_header": "core/CoreExport.h",
         "options": [
             {
@@ skipping 20 matching lines @@
             {
                 "domain": "DeviceOrientation"
             },
             {
                 "domain": "DOM"
             },
             {
                 "domain": "DOMDebugger"
             },
             {
+                "domain": "DOMSnapshot"
+            },
+            {
                 "domain": "DOMStorage"
             },
             {
                 "domain": "IndexedDB",
                 "async": ["requestDatabaseNames", "requestDatabase", "requestData", "clearObjectStore", "deleteDatabase"]
             },
             {
                 "domain": "LayerTree"
             },
             {
@@ skipping 68 matching lines @@
     },
 
     "lib": {
         "package": "core/inspector/protocol",
         "output": "inspector/protocol",
         "string_header": "core/inspector/V8InspectorString.h",
         "export_macro": "CORE_EXPORT",
         "export_header": "core/CoreExport.h"
     }
 }