Added showing slow scroll rectangles in Layers panel.

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 3826 matching lines @@
                 "id": "LayerId",
                 "type": "string",
                 "description": "Unique RenderLayer identifier."
             },
             {
                 "id": "SnapshotId",
                 "type": "string",
                 "description": "Unique snapshot identifier."
             },
             {
+                "id": "ScrollRect",
+                "type": "object",
+                "description": "Rectangle where scrolling happens on the main thread.",
+                "properties": [
+                    { "name": "rect", "$ref": "DOM.Rect", "description": "Rectangle itself." },
+                    { "name": "type", "type": "string", "enum": ["RepaintsOnScroll", "TouchEventHandler", "WheelEventHandler"], "description": "Reason for rectangle to force scrolling on the main thread" }
+                ]
+            },
+            {
                 "id": "Layer",
                 "type": "object",
                 "description": "Information about a compositing layer.",
                 "properties": [
                     { "name": "layerId", "$ref": "LayerId", "description": "The unique id for this layer." },
                     { "name": "parentLayerId", "$ref": "LayerId", "optional": true, "description": "The id of parent (not present for root)." },
                     { "name": "nodeId", "$ref": "DOM.NodeId", "optional": true, "description": "The id for the node associated with this layer." },
                     { "name": "offsetX", "type": "number", "description": "Offset from parent layer, X coordinate." },
                     { "name": "offsetY", "type": "number", "description": "Offset from parent layer, X coordinate." },
                     { "name": "width", "type": "number", "description": "Layer width." },
                     { "name": "height", "type": "number", "description": "Layer height." },
                     { "name": "transform", "type": "array", "items": { "type": "number" }, "minItems": 16, "maxItems": 16, "optional": true, "description": "Transformation matrix for layer, default is identity matrix" },
                     { "name": "anchorX", "type": "number", "optional": true, "description": "Transform anchor point X, absent if no transform specified" },
                     { "name": "anchorY", "type": "number", "optional": true, "description": "Transform anchor point Y, absent if no transform specified" },
                     { "name": "anchorZ", "type": "number", "optional": true, "description": "Transform anchor point Z, absent if no transform specified" },
                     { "name": "paintCount", "type": "integer", "description": "Indicates how many time this layer has painted." },
-                    { "name": "invisible", "type": "boolean", "optional": true, "description": "Set if layer is not visible." }
+                    { "name": "invisible", "type": "boolean", "optional": true, "description": "Set if layer is not visible." },
+                    { "name": "scrollRects", "type": "array", "items": { "$ref": "ScrollRect"}, "optional": true, "description": "Rectangles scrolling on main thread only."}
                 ]
             },
             {
                 "id": "PaintProfile",
                 "type": "array",
                 "description": "Array of timings, one per paint step.",
                 "items": {
                     "type": "number",
                     "description": "A time in seconds since the end of previous step (for the first step, time since painting started)"
                 }
@@ skipping 189 matching lines @@
             {
                 "name": "dataAvailable",
                 "parameters": [
                     {"name": "value", "type": "array", "items": { "$ref": "PowerEvent" }, "description": "List of power events." }
                 ],
                 "handlers": ["browser", "frontend"]
             }
         ]
     }]
 }