add customized printing setting for headless

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

 {
     "version": { "major": "1", "minor": "2" },
     "domains": [{
         "domain": "Inspector",
         "experimental": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 411 matching lines @@
                     { "name": "quality", "type": "integer", "optional": true, "description": "Compression quality from range [0..100] (jpeg only)." },
                     { "name": "fromSurface", "type": "boolean", "optional": true, "description": "Capture the screenshot from the surface, rather than the view. Defaults to false.", "experimental": true }
                 ],
                 "returns": [
                     { "name": "data", "type": "string", "description": "Base64-encoded image data." }
                 ],
                 "experimental": true
             },
             {
                 "name": "printToPDF",
                 "description": "Print page as pdf.",

[Lei Zhang, 2017/05/04 07:29:38]

BTW, write "PDF" because it expands out to Portable Document Format.

[jzfeng, 2017/05/05 02:41:34]

Done.

+                "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 colors. Defaults to false."},

[Lei Zhang, 2017/05/04 07:29:38]

Write "background graphics" to be more correct, and consistent with the phrase
used in print preview. It's more than just colors.

[jzfeng, 2017/05/05 02:41:34]

Done.

+                    {"name": "scale", "type": "number", "optional": true, "description": "Scale of the pdf. Defaults to 1."},

[Lei Zhang, 2017/05/04 07:29:38]

The description is a bit confusing. Does this mean if scale = 2, then an A4
portrait page will be scaled up to A2? It's really the scale of the webpage
rendering, or something like that.

[jzfeng, 2017/05/05 02:41:34]

Done.

+                    {"name": "paperWidth", "type": "number", "optional": true, "description": "Paper width in inch. Defaults to 8.5 inch."},

[Lei Zhang, 2017/05/04 07:29:38]

inches, ditto everywhere below.

[jzfeng, 2017/05/05 02:41:34]

Done.

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

Still need to write inches in a bunch of places.

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

Do you mean I should also use inches in "in inch"? I thought I only need to
change the ones after a number.
Done now.

[Lei Zhang, 2017/05/05 04:40:17]

Yes, as in Q: "What is the unit of measure?" A: "We measure the paper width in
inches."

+                    {"name": "paperHeight", "type": "number", "optional": true, "description": "Paper height. Defaults to 11 inch."},
+                    {"name": "marginTop", "type": "number", "optional": true, "description": "Top margin in inch. Defaults to 1cm = ~2/5 of an inch."},

[Lei Zhang, 2017/05/04 07:29:38]

Just write "Defaults to 1 cm. (~0.4 inches)"

[jzfeng, 2017/05/05 02:41:34]

Done.

+                    {"name": "marginBottom", "type": "number", "optional": true, "description": "Bottom margin in inch. Defaults to 1cm = ~2/5 of an inch."},
+                    {"name": "marginLeft", "type": "number", "optional": true, "description": "Left margin in inch. Defaults to 1cm = ~2/5 of an inch."},
+                    {"name": "marginRight", "type": "number", "optional": true, "description": "Right margin in inch. Defaults to 1cm = ~2/5 of an inch."},
+                    {"name": "pageRanges", "type": "string", "optional": true, "description": "Paper ranges to print, e.g., '1-5, 8, 11-13'. Defaults to print all pages."}

[Lei Zhang, 2017/05/04 07:29:38]

Defaults to the empty string, which means print all pages.

[jzfeng, 2017/05/05 02:41:34]

Done.

+                ],
                 "returns": [
                     { "name": "data", "type": "string", "description": "Base64-encoded pdf data." }
                 ],
                 "experimental": true
             },
             {
                 "name": "startScreencast",
                 "description": "Starts sending each frame using the <code>screencastFrame</code> event.",
                 "parameters": [
                     { "name": "format", "type": "string", "optional": true, "enum": ["jpeg", "png"], "description": "Image compression format." },
@@ skipping 4206 matching lines @@
                 "parameters": [
                     { "name": "windowId", "$ref": "WindowID", "description": "Browser window id." }
                 ],
                 "returns": [
                     { "name": "bounds", "$ref": "Bounds", "description": "Bounds information of the window. When window state is 'minimized', the restored window position and size are returned." }
                 ]
             }
         ]
     }]
 }