add customized printing setting for headless

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

Index: third_party/WebKit/Source/core/inspector/browser_protocol.json
diff --git a/third_party/WebKit/Source/core/inspector/browser_protocol.json b/third_party/WebKit/Source/core/inspector/browser_protocol.json
index ccc2d2b3bd2516d1cf26cac51ef0bef53e2daa0f..480b21b55408574846b9dd6940e8554554f477db 100644
--- a/third_party/WebKit/Source/core/inspector/browser_protocol.json
+++ b/third_party/WebKit/Source/core/inspector/browser_protocol.json
@@ -429,7 +429,20 @@
             },
             {
                 "name": "printToPDF",
-                "description": "Print page as pdf.",
+                "description": "Print page as PDF.",
+                "parameters": [
+                    {"name": "landscape", "type": "boolean", "optional": true, "description": "Paper orientation. Defaults to false."},
+                    {"name": "displayHeaderFooter", "type": "boolean", "optional": true, "description": "Display header and footer. Defaults to false."},
+                    {"name": "printBackgrounds", "type": "boolean", "optional": true, "description": "Print background graphics. Defaults to false."},

[Lei Zhang, 2017/05/05 03:53:00]

printBackground

[jzfeng, 2017/05/05 04:28:10]

Done.

+                    {"name": "scale", "type": "number", "optional": true, "description": "Scale of the webpage rendering. Defaults to 1."},
+                    {"name": "paperWidth", "type": "number", "optional": true, "description": "Paper width in inch. Defaults to 8.5 inches."},
+                    {"name": "paperHeight", "type": "number", "optional": true, "description": "Paper height. Defaults to 11 inches."},
+                    {"name": "marginTop", "type": "number", "optional": true, "description": "Top margin in inch. Defaults to 1cm (~0.4 inches)."},
+                    {"name": "marginBottom", "type": "number", "optional": true, "description": "Bottom margin in inch. Defaults to 1cm (~0.4 inches)."},
+                    {"name": "marginLeft", "type": "number", "optional": true, "description": "Left margin in inch. Defaults to 1cm (~0.4 inches)."},
+                    {"name": "marginRight", "type": "number", "optional": true, "description": "Right margin in inch. Defaults to 1cm (~0.4 inches)."},
+                    {"name": "pageRanges", "type": "string", "optional": true, "description": "Paper ranges to print, e.g., '1-5, 8, 11-13'. Defaults to the empty string, which means print all pages."}
+                ],
                 "returns": [
                     { "name": "data", "type": "string", "description": "Base64-encoded pdf data." }
                 ],