DevTools: optimize screencast for slower devices.

third_party/WebKit/Source/devtools/protocol.json

Index: third_party/WebKit/Source/devtools/protocol.json
diff --git a/third_party/WebKit/Source/devtools/protocol.json b/third_party/WebKit/Source/devtools/protocol.json
index 813bb5d13ca10c3c4fecf248b4efc231b68a43f9..5045cf2eb461f5b8eb16dac25e86b04e177d91bc 100644
--- a/third_party/WebKit/Source/devtools/protocol.json
+++ b/third_party/WebKit/Source/devtools/protocol.json
@@ -413,7 +413,8 @@
                     { "name": "format", "type": "string", "optional": true, "enum": ["jpeg", "png"], "description": "Image compression format." },
                     { "name": "quality", "type": "integer", "optional": true, "description": "Compression quality from range [0..100]." },
                     { "name": "maxWidth", "type": "integer", "optional": true, "description": "Maximum screenshot width." },
-                    { "name": "maxHeight", "type": "integer", "optional": true, "description": "Maximum screenshot height." }
+                    { "name": "maxHeight", "type": "integer", "optional": true, "description": "Maximum screenshot height." },
+                    { "name": "everyNthFrame", "type": "integer", "optional": true, "description": "Send every n-th frame." }
                 ],
                 "hidden": true,
                 "handlers": ["browser", "renderer"]