Adds scroll position/scale emulation to DevTools.

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

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications.",
@@ skipping 657 matching lines @@
                 "description": "Screen orientation.",
                 "properties": [
                     { "name": "type",  "type": "string", "enum": ["portraitPrimary", "portraitSecondary", "landscapePrimary", "landscapeSecondary"], "description": "Orientation type." },
                     { "name": "angle",  "type": "integer", "description": "Orientation angle." }
                 ]
             }
         ],
         "commands": [
             {
                 "name": "setDeviceMetricsOverride",
-                "description": "Overrides the values of device screen dimensions (window.screen.width, window.screen.height, window.innerWidth, window.innerHeight, and \"device-width\"/\"device-height\"-related CSS media query results).",
+                "description": "Overrides the values of device, screen, and viewport dimensions and positions (including window.screen.width, window.screen.height, window.innerWidth, window.innerHeight, and \"device-width\"/\"device-height\"-related CSS media query results).",
                 "parameters": [
                     { "name": "width", "type": "integer", "description": "Overriding width value in pixels (minimum 0, maximum 10000000). 0 disables the override." },
                     { "name": "height", "type": "integer", "description": "Overriding height value in pixels (minimum 0, maximum 10000000). 0 disables the override." },
                     { "name": "deviceScaleFactor", "type": "number", "description": "Overriding device scale factor value. 0 disables the override." },
                     { "name": "mobile", "type": "boolean", "description": "Whether to emulate mobile device. This includes viewport meta tag, overlay scrollbars, text autosizing and more." },
                     { "name": "fitWindow", "type": "boolean", "description": "Whether a view that exceeds the available browser window area should be scaled down to fit." },
                     { "name": "scale", "type": "number", "optional": true, "description": "Scale to apply to resulting view image. Ignored in |fitWindow| mode." },
                     { "name": "offsetX", "type": "number", "optional": true, "description": "X offset to shift resulting view image by. Ignored in |fitWindow| mode." },
                     { "name": "offsetY", "type": "number", "optional": true, "description": "Y offset to shift resulting view image by. Ignored in |fitWindow| mode." },
                     { "name": "screenWidth", "type": "integer", "optional": true, "description": "Overriding screen width value in pixels (minimum 0, maximum 10000000). Only used for |mobile==true|." },
                     { "name": "screenHeight", "type": "integer", "optional": true, "description": "Overriding screen height value in pixels (minimum 0, maximum 10000000). Only used for |mobile==true|." },
                     { "name": "positionX", "type": "integer", "optional": true, "description": "Overriding view X position on screen in pixels (minimum 0, maximum 10000000). Only used for |mobile==true|." },
                     { "name": "positionY", "type": "integer", "optional": true, "description": "Overriding view Y position on screen in pixels (minimum 0, maximum 10000000). Only used for |mobile==true|." },
-                    { "name": "screenOrientation", "$ref": "ScreenOrientation", "optional": true, "description": "Screen orientation override." }
+                    { "name": "screenOrientation", "$ref": "ScreenOrientation", "optional": true, "description": "Screen orientation override." },
+                    { "name": "scrollPositionX", "type": "integer", "optional": true, "description": "Fix horizontal scroll position of outer viewport (frame) to an override value (device-independent pixel)." },

[bokan, 2016/07/04 22:44:09]

The `outer`/`inner` terminology is specific to the compositor. Outside it we
just use `layout` and `visual`.

[Eric Seckler, 2016/07/05 16:46:51]

Done, also in WebDeviceEmulationParams.

+                    { "name": "scrollPositionY", "type": "integer", "optional": true, "description": "Fix  vertical scroll position of outer viewport (frame) to an override value (device-independent pixel)." },
+                    { "name": "visualViewportWidth", "type": "integer", "optional": true, "description": "Override height of inner (visual) viewport (pixels, minimum 0, maximum 10000000). Optional, defaults to |width|." },
+                    { "name": "visualViewportHeight", "type": "integer", "optional": true, "description": "Override height of inner (visual) viewport (pixels, minimum 0, maximum 10000000). Optional, defaults to |height|." },
+                    { "name": "visualViewportPositionX", "type": "number", "optional": true, "description": "Fix horizontal scroll position of inner (visual) viewport to an override value (partial device-independent pixels, relative to |scrollPositionX|)." },
+                    { "name": "visualViewportPositionY", "type": "number", "optional": true, "description": "Fix vertical scroll position of inner (visual) viewport to an override value (partial device-independent pixels, relative to |scrollPositionY|)." },
+                    { "name": "visualViewportScale", "type": "number", "optional": true, "description": "Fix pinch-zoom scale of the inner (visual) viewport to an override value (0 < value <= 10.0, 1.0 is default-scale)." }
                 ],
                 "handlers": ["browser"]
             },
             {
                 "name": "clearDeviceMetricsOverride",
                 "description": "Clears the overriden device metrics.",
                 "handlers": ["browser"]
             },
             {
                 "name": "resetPageScaleFactor",
@@ skipping 3523 matching lines @@
                 "description": "Dispatches protocol message from the target with given id.",
                 "parameters": [
                     { "name": "targetId", "$ref": "TargetID" },
                     { "name": "message", "type": "string" }
                 ],
                 "handlers": ["browser"]
             }
         ]
     }]
 }