Adds DevTools commands for forced viewport override.

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 cf7c9d0d2ef540953d515c60dab978c5a55f5e6f..27f526895316361260effc928bc9348b6e90c26e 100644
--- a/third_party/WebKit/Source/core/inspector/browser_protocol.json
+++ b/third_party/WebKit/Source/core/inspector/browser_protocol.json
@@ -730,9 +730,9 @@
                     { "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": "scale", "type": "number", "optional": true, "deprecated": true, "description": "Not used." },

[dgozman, 2016/08/22 22:22:06]

Please leave the scale, it's used by DevTools.

[Eric Seckler, 2016/08/23 09:32:19]

Ah, misunderstood you. Is it missing tests? (I didn't see anything under
inspector/ or inspector-protocol/ breaking.)

+                    { "name": "offsetX", "type": "number", "optional": true, "deprecated": true, "description": "Not used." },
+                    { "name": "offsetY", "type": "number", "optional": true, "deprecated": true, "description": "Not used." },
                     { "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|." },
@@ -747,6 +747,19 @@
                 "handlers": ["browser"]
             },
             {
+                "name": "forceViewport",
+                "description": "Overrides the visible area of the page. The change is hidden from the page, i.e. the observable scroll position and page scale does not change. In effect, the command moves the specified area of the page into the top-left corner of the frame.",
+                "parameters": [
+                    { "name": "x", "type": "number", "description": "X coordinate of top-left corner of the area (CSS pixels)." },
+                    { "name": "y", "type": "number", "description": "Y coordinate of top-left corner of the area (CSS pixels)." },
+                    { "name": "scale", "type": "number", "optional": true, "description": "Scale to apply to the area (relative to a page scale of 1.0). Defaults to 1.0." }

[chrishtr, 2016/08/22 22:00:42]

What is the origin of this scale?

[Eric Seckler, 2016/08/23 09:32:19]

It's relative to a page scale of 1.0 and effectively overrides the page scale.
We'll be using this to e.g. create thumbnail screenshots (or e.g. "zoomed"
screenshots of elements on a page). The reason we're supplying it here rather
than setting it with via setPageScaleFactor is that changes to the page scale
factor are visible to the page (e.g. through window.innerWidth/Height), so we're
instead adapting to changes in the page scale.

+                ]
+            },
+            {
+                "name": "resetViewport",
+                "description": "Resets the visible area of the page to the original viewport, undoing any effects of the forceViewport command."
+            },
+            {
                 "name": "resetPageScaleFactor",
                 "description": "Requests that page scale factor is reset to initial values."
             },