6 files changed, 1062 insertions, 0 deletions
diff --git a/gfx/layers/layerviewer/hide.png b/gfx/layers/layerviewer/hide.png
new file mode 100644
index 0000000000..9a92e2c1b1
--- /dev/null
+++ b/gfx/layers/layerviewer/hide.png
diff --git a/gfx/layers/layerviewer/index.html b/gfx/layers/layerviewer/index.html
new file mode 100644
index 0000000000..000e40b8bd
--- /dev/null
+++ b/gfx/layers/layerviewer/index.html
@@ -0,0 +1,51 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>GFX Display List & Layer Visualizer</title>
+    <meta charset="utf-8">
+    <link rel="stylesheet" type="text/css" href="tree.css">
+    <script src="layerTreeView.js"></script>
+    <style>
+
+.csstooltip
+{
+  z-index: 5;
+  background: white;
+  border: solid 1px black;
+  position: absolute;
+  padding: 5px;
+  margin: 5px;
+  max-width: 300px;
+}
+    </style>
+  </head>
+  <body>
+    <h1>GFX Layers dump visualizer:</h1>
+    Paste your display list or layers dump into this textarea:<br>
+    <textarea id="input_layers_dump" style="width:100%; height: 80%;" cols="80" rows="10">
+ClientLayerManager (0x1264f5000)
+  ClientContainerLayer (0x1263fe200) [visible=< (x=0, y=0, w=1457, h=1163); >] [opaqueContent] [metrics0={ [cb=(x=0.000000, y=0.000000, w=1457.000000, h=1163.000000)] [sr=(x=0.000000, y=0.000000, w=1457.000000, h=1163.000000)] [s=(0,0)] [dp=(x=0.000000, y=0.000000, w=1457.000000, h=1163.000000)] [cdp=(x=0.000000, y=0.000000, w=0.000000, h=0.000000)] [color=rgba(0, 0, 0, 0.000000)] [scrollId=3] [z=1] }]
+    ClientTiledPaintedLayer (0x1263b3600) [bounds=(x=-1, y=0, w=1458, h=1163)] [visible=< (x=0, y=0, w=1457, h=79); >] { hitregion=< (x=0, y=0, w=1457, h=47); (x=-1, y=47, w=1458, h=24); (x=0, y=71, w=1457, h=1092); > dispatchtocontentregion=< (x=68, y=9, w=1375, h=31); (x=944, y=47, w=280, h=24); >} [opaqueContent] [valid=< (x=0, y=0, w=1457, h=79); >]
+      SingleTiledContentClient (0x126f80680)
+    ClientContainerLayer (0x122a33f00) [clip=(x=0, y=79, w=1457, h=1084)] [visible=< (x=0, y=79, w=1457, h=1084); >] [opaqueContent]
+      ClientTiledPaintedLayer (0x11e11a700) [bounds=(x=0, y=79, w=1457, h=1084)] [visible=< (x=0, y=79, w=1457, h=1084); >] { hitregion=< (x=0, y=79, w=1457, h=1084); > dispatchtocontentregion=< (x=0, y=125, w=1457, h=1034); >} [opaqueContent] [valid=< (x=0, y=79, w=1457, h=1084); >]
+        SingleTiledContentClient (0x1226d52c0)
+    </textarea>
+    <br>
+    <input type="button" value="Process pasted log" onclick="log_pasted()" />
+    <br>
+    <br>
+    Help: To get a layers dump go to about:config and set layout.display-list.dump;true or layers.dump;true.
+    <script>
+function log_pasted() {
+  var container = parseMultiLineDump(document.getElementById("input_layers_dump").value);
+  document.body.innerHTML = "";
+  document.body.appendChild(container);
+}
+    </script>
+  </body>
+</html>
diff --git a/gfx/layers/layerviewer/layerTreeView.js b/gfx/layers/layerviewer/layerTreeView.js
new file mode 100644
index 0000000000..5cf21c71b4
--- /dev/null
+++ b/gfx/layers/layerviewer/layerTreeView.js
@@ -0,0 +1,972 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function toFixed(num, fixed) {
+  fixed = fixed || 0;
+  fixed = Math.pow(10, fixed);
+  return Math.floor(num * fixed) / fixed;
+}
+function createElement(name, props) {
+  var el = document.createElement(name);
+
+  for (var key in props) {
+    if (key === "style") {
+      for (var styleName in props.style) {
+        el.style[styleName] = props.style[styleName];
+      }
+    } else {
+      el[key] = props[key];
+    }
+  }
+
+  return el;
+}
+
+function parseDisplayList(lines) {
+  var root = {
+    line: "DisplayListRoot 0",
+    name: "DisplayListRoot",
+    address: "0x0",
+    frame: "Root",
+    children: [],
+  };
+
+  var objectAtIndentation = {
+    "-1": root,
+  };
+
+  for (var i = 0; i < lines.length; i++) {
+    var line = lines[i];
+
+    var layerObject = {
+      line,
+      children: [],
+    };
+    if (!root) {
+      root = layerObject;
+    }
+
+    var matches = line.match(
+      "(\\s*)(\\w+)\\sp=(\\w+)\\sf=(.*?)\\((.*?)\\)\\s(z=(\\w+)\\s)?(.*?)?( layer=(\\w+))?$"
+    );
+    if (!matches) {
+      dump("Failed to match: " + line + "\n");
+      continue;
+    }
+
+    var indentation = Math.floor(matches[1].length / 2);
+    objectAtIndentation[indentation] = layerObject;
+    var parent = objectAtIndentation[indentation - 1];
+    if (parent) {
+      parent.children.push(layerObject);
+    }
+
+    layerObject.name = matches[2];
+    layerObject.address = matches[3]; // Use 0x prefix to be consistent with layer dump
+    layerObject.frame = matches[4];
+    layerObject.contentDescriptor = matches[5];
+    layerObject.z = matches[7];
+    var rest = matches[8];
+    if (matches[10]) {
+      // WrapList don't provide a layer
+      layerObject.layer = matches[10];
+    }
+    layerObject.rest = rest;
+
+    // the content node name doesn't have a prefix, this makes the parsing easier
+    rest = "content" + rest;
+
+    var nesting = 0;
+    var startIndex;
+    var lastSpace = -1;
+    for (var j = 0; j < rest.length; j++) {
+      if (rest.charAt(j) == "(") {
+        nesting++;
+        if (nesting == 1) {
+          startIndex = j;
+        }
+      } else if (rest.charAt(j) == ")") {
+        nesting--;
+        if (nesting == 0) {
+          var name = rest.substring(lastSpace + 1, startIndex);
+          var value = rest.substring(startIndex + 1, j);
+
+          var rectMatches = value.match("^(.*?),(.*?),(.*?),(.*?)$");
+          if (rectMatches) {
+            layerObject[name] = [
+              parseFloat(rectMatches[1]),
+              parseFloat(rectMatches[2]),
+              parseFloat(rectMatches[3]),
+              parseFloat(rectMatches[4]),
+            ];
+          } else {
+            layerObject[name] = value;
+          }
+        }
+      } else if (nesting == 0 && rest.charAt(j) == " ") {
+        lastSpace = j;
+      }
+    }
+    // dump("FIELDS: " + JSON.stringify(fields) + "\n");
+  }
+  return root;
+}
+
+function trim(s) {
+  return (s || "").replace(/^\s+|\s+$/g, "");
+}
+
+function getDataURI(str) {
+  if (str.indexOf("data:image/png;base64,") == 0) {
+    return str;
+  }
+
+  var matches = str.match(
+    "data:image/lz4bgra;base64,([0-9]+),([0-9]+),([0-9]+),(.*)"
+  );
+  if (!matches) {
+    return null;
+  }
+
+  var canvas = document.createElement("canvas");
+  var w = parseInt(matches[1]);
+  var stride = parseInt(matches[2]);
+  var h = parseInt(matches[3]);
+  canvas.width = w;
+  canvas.height = h;
+
+  // TODO handle stride
+
+  var binary_string = window.atob(matches[4]);
+  var len = binary_string.length;
+  var bytes = new Uint8Array(len);
+  var decoded = new Uint8Array(stride * h);
+  for (var i = 0; i < len; i++) {
+    var ascii = binary_string.charCodeAt(i);
+    bytes[i] = ascii;
+  }
+
+  var ctxt = canvas.getContext("2d");
+  var out = ctxt.createImageData(w, h);
+  // This is actually undefined throughout the tree and it isn't clear what it
+  // should be. Since this is only development code, leave it alone for now.
+  // eslint-disable-next-line no-undef
+  LZ4_uncompressChunk(bytes, decoded);
+
+  for (var x = 0; x < w; x++) {
+    for (var y = 0; y < h; y++) {
+      out.data[4 * x + 4 * y * w + 0] = decoded[4 * x + y * stride + 2];
+      out.data[4 * x + 4 * y * w + 1] = decoded[4 * x + y * stride + 1];
+      out.data[4 * x + 4 * y * w + 2] = decoded[4 * x + y * stride + 0];
+      out.data[4 * x + 4 * y * w + 3] = decoded[4 * x + y * stride + 3];
+    }
+  }
+
+  ctxt.putImageData(out, 0, 0);
+  return canvas.toDataURL();
+}
+
+function parseLayers(layersDumpLines) {
+  function parseMatrix2x3(str) {
+    str = trim(str);
+
+    // Something like '[ 1 0; 0 1; 0 158; ]'
+    var matches = str.match("^\\[ (.*?) (.*?); (.*?) (.*?); (.*?) (.*?); \\]$");
+    if (!matches) {
+      return null;
+    }
+
+    var matrix = [
+      [parseFloat(matches[1]), parseFloat(matches[2])],
+      [parseFloat(matches[3]), parseFloat(matches[4])],
+      [parseFloat(matches[5]), parseFloat(matches[6])],
+    ];
+
+    return matrix;
+  }
+  function parseColor(str) {
+    str = trim(str);
+
+    // Something like 'rgba(0, 0, 0, 0)'
+    var colorMatches = str.match("^rgba\\((.*), (.*), (.*), (.*)\\)$");
+    if (!colorMatches) {
+      return null;
+    }
+
+    var color = {
+      r: colorMatches[1],
+      g: colorMatches[2],
+      b: colorMatches[3],
+      a: colorMatches[4],
+    };
+    return color;
+  }
+  function parseFloat_cleo(str) {
+    str = trim(str);
+
+    // Something like 2.000
+    if (parseFloat(str) == str) {
+      return parseFloat(str);
+    }
+
+    return null;
+  }
+  function parseRect2D(str) {
+    str = trim(str);
+
+    // Something like '(x=0, y=0, w=2842, h=158)'
+    var rectMatches = str.match("^\\(x=(.*?), y=(.*?), w=(.*?), h=(.*?)\\)$");
+    if (!rectMatches) {
+      return null;
+    }
+
+    var rect = [
+      parseFloat(rectMatches[1]),
+      parseFloat(rectMatches[2]),
+      parseFloat(rectMatches[3]),
+      parseFloat(rectMatches[4]),
+    ];
+    return rect;
+  }
+  function parseRegion(str) {
+    str = trim(str);
+
+    // Something like '< (x=0, y=0, w=2842, h=158); (x=0, y=1718, w=2842, h=500); >'
+    if (str.charAt(0) != "<" || str.charAt(str.length - 1) != ">") {
+      return null;
+    }
+
+    var region = [];
+    str = trim(str.substring(1, str.length - 1));
+    while (str != "") {
+      var rectMatches = str.match(
+        "^\\(x=(.*?), y=(.*?), w=(.*?), h=(.*?)\\);(.*)$"
+      );
+      if (!rectMatches) {
+        return null;
+      }
+
+      var rect = [
+        parseFloat(rectMatches[1]),
+        parseFloat(rectMatches[2]),
+        parseFloat(rectMatches[3]),
+        parseFloat(rectMatches[4]),
+      ];
+      str = trim(rectMatches[5]);
+      region.push(rect);
+    }
+    return region;
+  }
+
+  var LAYERS_LINE_REGEX = "(\\s*)(\\w+)\\s\\((\\w+)\\)(.*)";
+
+  var root;
+  var objectAtIndentation = [];
+  for (var i = 0; i < layersDumpLines.length; i++) {
+    // Something like 'ThebesLayerComposite (0x12104cc00) [shadow-visible=< (x=0, y=0, w=1920, h=158); >] [visible=< (x=0, y=0, w=1920, h=158); >] [opaqueContent] [valid=< (x=0, y=0, w=1920, h=2218); >]'
+    var line = layersDumpLines[i].name || layersDumpLines[i];
+
+    var tileMatches = line.match("(\\s*)Tile \\(x=(.*), y=(.*)\\): (.*)");
+    if (tileMatches) {
+      let indentation = Math.floor(matches[1].length / 2);
+      var x = tileMatches[2];
+      var y = tileMatches[3];
+      var dataUri = tileMatches[4];
+      let parent = objectAtIndentation[indentation - 1];
+      var tiles = parent.tiles || {};
+
+      tiles[x] = tiles[x] || {};
+      tiles[x][y] = dataUri;
+
+      parent.tiles = tiles;
+
+      continue;
+    }
+
+    var surfaceMatches = line.match("(\\s*)Surface: (.*)");
+    if (surfaceMatches) {
+      let indentation = Math.floor(matches[1].length / 2);
+      let parent =
+        objectAtIndentation[indentation - 1] ||
+        objectAtIndentation[indentation - 2];
+
+      var surfaceURI = surfaceMatches[2];
+      if (parent.surfaceURI != null) {
+        console.log(
+          "error: surfaceURI already set for this layer " + parent.line
+        );
+      }
+      parent.surfaceURI = surfaceURI;
+
+      // Look for the buffer-rect offset
+      var contentHostLine =
+        layersDumpLines[i - 2].name || layersDumpLines[i - 2];
+      let matches = contentHostLine.match(LAYERS_LINE_REGEX);
+      if (matches) {
+        var contentHostRest = matches[4];
+        parent.contentHostProp = {};
+        parseProperties(contentHostRest, parent.contentHostProp);
+      }
+
+      continue;
+    }
+
+    var layerObject = {
+      line,
+      children: [],
+    };
+    if (!root) {
+      root = layerObject;
+    }
+
+    let matches = line.match(LAYERS_LINE_REGEX);
+    if (!matches) {
+      continue; // Something like a texturehost dump. Safe to ignore
+    }
+
+    if (
+      matches[2].includes("TiledContentHost") ||
+      matches[2].includes("ContentHost") ||
+      matches[2].includes("ContentClient") ||
+      matches[2].includes("MemoryTextureHost") ||
+      matches[2].includes("ImageHost")
+    ) {
+      continue; // We're already pretty good at visualizing these
+    }
+
+    var indentation = Math.floor(matches[1].length / 2);
+    objectAtIndentation[indentation] = layerObject;
+    for (var c = indentation + 1; c < objectAtIndentation.length; c++) {
+      objectAtIndentation[c] = null;
+    }
+    if (indentation > 0) {
+      var parent = objectAtIndentation[indentation - 1];
+      while (!parent) {
+        indentation--;
+        parent = objectAtIndentation[indentation - 1];
+      }
+
+      parent.children.push(layerObject);
+    }
+
+    layerObject.name = matches[2];
+    layerObject.address = matches[3];
+
+    var rest = matches[4];
+
+    function parseProperties(rest, layerObject) {
+      var fields = [];
+      var nesting = 0;
+      var startIndex;
+      for (let j = 0; j < rest.length; j++) {
+        if (rest.charAt(j) == "[") {
+          nesting++;
+          if (nesting == 1) {
+            startIndex = j;
+          }
+        } else if (rest.charAt(j) == "]") {
+          nesting--;
+          if (nesting == 0) {
+            fields.push(rest.substring(startIndex + 1, j));
+          }
+        }
+      }
+
+      for (let j = 0; j < fields.length; j++) {
+        // Something like 'valid=< (x=0, y=0, w=1920, h=2218); >' or 'opaqueContent'
+        var field = fields[j];
+        // dump("FIELD: " + field + "\n");
+        var parts = field.split("=", 2);
+        var fieldName = parts[0];
+        rest = field.substring(fieldName.length + 1);
+        if (parts.length == 1) {
+          layerObject[fieldName] = "true";
+          layerObject[fieldName].type = "bool";
+          continue;
+        }
+        var float = parseFloat_cleo(rest);
+        if (float) {
+          layerObject[fieldName] = float;
+          layerObject[fieldName].type = "float";
+          continue;
+        }
+        var region = parseRegion(rest);
+        if (region) {
+          layerObject[fieldName] = region;
+          layerObject[fieldName].type = "region";
+          continue;
+        }
+        var rect = parseRect2D(rest);
+        if (rect) {
+          layerObject[fieldName] = rect;
+          layerObject[fieldName].type = "rect2d";
+          continue;
+        }
+        var matrix = parseMatrix2x3(rest);
+        if (matrix) {
+          layerObject[fieldName] = matrix;
+          layerObject[fieldName].type = "matrix2x3";
+          continue;
+        }
+        var color = parseColor(rest);
+        if (color) {
+          layerObject[fieldName] = color;
+          layerObject[fieldName].type = "color";
+          continue;
+        }
+        if (rest[0] == "{" && rest[rest.length - 1] == "}") {
+          var object = {};
+          parseProperties(rest.substring(1, rest.length - 2).trim(), object);
+          layerObject[fieldName] = object;
+          layerObject[fieldName].type = "object";
+          continue;
+        }
+        fieldName = fieldName.split(" ")[0];
+        layerObject[fieldName] = rest[0];
+        layerObject[fieldName].type = "string";
+      }
+    }
+    parseProperties(rest, layerObject);
+
+    if (!layerObject["shadow-transform"]) {
+      // No shadow transform = identify
+      layerObject["shadow-transform"] = [
+        [1, 0],
+        [0, 1],
+        [0, 0],
+      ];
+    }
+
+    // Compute screenTransformX/screenTransformY
+    // TODO Fully support transforms
+    if (layerObject["shadow-transform"] && layerObject.transform) {
+      layerObject["screen-transform"] = [
+        layerObject["shadow-transform"][2][0],
+        layerObject["shadow-transform"][2][1],
+      ];
+      var currIndentation = indentation - 1;
+      while (currIndentation >= 0) {
+        var transform =
+          objectAtIndentation[currIndentation]["shadow-transform"] ||
+          objectAtIndentation[currIndentation].transform;
+        if (transform) {
+          layerObject["screen-transform"][0] += transform[2][0];
+          layerObject["screen-transform"][1] += transform[2][1];
+        }
+        currIndentation--;
+      }
+    }
+
+    // dump("Fields: " + JSON.stringify(fields) + "\n");
+  }
+  root.compositeTime = layersDumpLines.compositeTime;
+  // dump("OBJECTS: " + JSON.stringify(root) + "\n");
+  return root;
+}
+function populateLayers(
+  root,
+  displayList,
+  pane,
+  previewParent,
+  hasSeenRoot,
+  contentScale,
+  rootPreviewParent
+) {
+  contentScale = contentScale || 1;
+  rootPreviewParent = rootPreviewParent || previewParent;
+
+  function getDisplayItemForLayer(displayList) {
+    var items = [];
+    if (!displayList) {
+      return items;
+    }
+    if (displayList.layer == root.address) {
+      items.push(displayList);
+    }
+    for (var i = 0; i < displayList.children.length; i++) {
+      var subDisplayItems = getDisplayItemForLayer(displayList.children[i]);
+      for (let j = 0; j < subDisplayItems.length; j++) {
+        items.push(subDisplayItems[j]);
+      }
+    }
+    return items;
+  }
+  var elem = createElement("div", {
+    className: "layerObjectDescription",
+    textContent: root.line,
+    style: {
+      whiteSpace: "pre",
+    },
+    onmouseover() {
+      if (this.layerViewport) {
+        this.layerViewport.classList.add("layerHover");
+      }
+    },
+    onmouseout() {
+      if (this.layerViewport) {
+        this.layerViewport.classList.remove("layerHover");
+      }
+    },
+  });
+  var icon = createElement("img", {
+    src: "show.png",
+    style: {
+      width: "12px",
+      height: "12px",
+      marginLeft: "4px",
+      marginRight: "4px",
+      cursor: "pointer",
+    },
+    onclick() {
+      if (this.layerViewport) {
+        if (this.layerViewport.style.visibility == "hidden") {
+          this.layerViewport.style.visibility = "";
+          this.src = "show.png";
+        } else {
+          this.layerViewport.style.visibility = "hidden";
+          this.src = "hide.png";
+        }
+      }
+    },
+  });
+  elem.insertBefore(icon, elem.firstChild);
+  pane.appendChild(elem);
+
+  if (root["shadow-visible"] || root.visible) {
+    var visibleRegion = root["shadow-visible"] || root.visible;
+    var layerViewport = createElement("div", {
+      id: root.address + "_viewport",
+      style: {
+        position: "absolute",
+        pointerEvents: "none",
+      },
+    });
+    elem.layerViewport = layerViewport;
+    icon.layerViewport = layerViewport;
+    var layerViewportMatrix = [1, 0, 0, 1, 0, 0];
+    if (root["shadow-clip"] || root.clip) {
+      var clip = root["shadow-clip"] || root.clip;
+      var clipElem = createElement("div", {
+        id: root.address + "_clip",
+        style: {
+          left: clip[0] + "px",
+          top: clip[1] + "px",
+          width: clip[2] + "px",
+          height: clip[3] + "px",
+          position: "absolute",
+          overflow: "hidden",
+          pointerEvents: "none",
+        },
+      });
+      layerViewportMatrix[4] += -clip[0];
+      layerViewportMatrix[5] += -clip[1];
+      layerViewport.style.transform =
+        "translate(-" + clip[0] + "px, -" + clip[1] + "px)";
+    }
+    if (root["shadow-transform"] || root.transform) {
+      var matrix = root["shadow-transform"] || root.transform;
+      layerViewportMatrix[0] = matrix[0][0];
+      layerViewportMatrix[1] = matrix[0][1];
+      layerViewportMatrix[2] = matrix[1][0];
+      layerViewportMatrix[3] = matrix[1][1];
+      layerViewportMatrix[4] += matrix[2][0];
+      layerViewportMatrix[5] += matrix[2][1];
+    }
+    layerViewport.style.transform =
+      "matrix(" +
+      layerViewportMatrix[0] +
+      "," +
+      layerViewportMatrix[1] +
+      "," +
+      layerViewportMatrix[2] +
+      "," +
+      layerViewportMatrix[3] +
+      "," +
+      layerViewportMatrix[4] +
+      "," +
+      layerViewportMatrix[5] +
+      ")";
+    if (!hasSeenRoot) {
+      hasSeenRoot = true;
+      layerViewport.style.transform =
+        "scale(" + 1 / contentScale + "," + 1 / contentScale + ")";
+    }
+    if (clipElem) {
+      previewParent.appendChild(clipElem);
+      clipElem.appendChild(layerViewport);
+    } else {
+      previewParent.appendChild(layerViewport);
+    }
+    previewParent = layerViewport;
+    for (let i = 0; i < visibleRegion.length; i++) {
+      let rect2d = visibleRegion[i];
+      var layerPreview = createElement("div", {
+        id: root.address + "_visible_part" + i + "-" + visibleRegion.length,
+        className: "layerPreview",
+        style: {
+          position: "absolute",
+          left: rect2d[0] + "px",
+          top: rect2d[1] + "px",
+          width: rect2d[2] + "px",
+          height: rect2d[3] + "px",
+          overflow: "hidden",
+          border: "solid 1px black",
+          background:
+            'url("noise.png"), linear-gradient(rgba(255, 255, 255, 0.5), rgba(255, 255, 255, 0.2))',
+        },
+      });
+      layerViewport.appendChild(layerPreview);
+
+      function isInside(rect1, rect2) {
+        if (
+          rect1[0] + rect1[2] < rect2[0] &&
+          rect2[0] + rect2[2] < rect1[0] &&
+          rect1[1] + rect1[3] < rect2[1] &&
+          rect2[1] + rect2[3] < rect1[1]
+        ) {
+          return true;
+        }
+        return true;
+      }
+
+      var hasImg = false;
+      // Add tile img objects for this part
+      var previewOffset = rect2d;
+
+      if (root.tiles) {
+        hasImg = true;
+        for (var x in root.tiles) {
+          for (var y in root.tiles[x]) {
+            if (isInside(rect2d, [x, y, 512, 512])) {
+              var tileImgElem = createElement("img", {
+                src: getDataURI(root.tiles[x][y]),
+                style: {
+                  position: "absolute",
+                  left: x - previewOffset[0] + "px",
+                  top: y - previewOffset[1] + "px",
+                  pointerEvents: "auto",
+                },
+              });
+              layerPreview.appendChild(tileImgElem);
+            }
+          }
+        }
+        layerPreview.style.background = "";
+      } else if (root.surfaceURI) {
+        hasImg = true;
+        var offsetX = 0;
+        var offsetY = 0;
+        if (root.contentHostProp && root.contentHostProp["buffer-rect"]) {
+          offsetX = root.contentHostProp["buffer-rect"][0];
+          offsetY = root.contentHostProp["buffer-rect"][1];
+        }
+        var surfaceImgElem = createElement("img", {
+          src: getDataURI(root.surfaceURI),
+          style: {
+            position: "absolute",
+            left: offsetX - previewOffset[0] + "px",
+            top: offsetY - previewOffset[1] + "px",
+            pointerEvents: "auto",
+          },
+        });
+        layerPreview.appendChild(surfaceImgElem);
+        layerPreview.style.background = "";
+      } else if (root.color) {
+        hasImg = true;
+        layerPreview.style.background =
+          "rgba(" +
+          root.color.r +
+          ", " +
+          root.color.g +
+          ", " +
+          root.color.b +
+          ", " +
+          root.color.a +
+          ")";
+      }
+
+      if (hasImg || true) {
+        layerPreview.mouseoverElem = elem;
+        layerPreview.onmouseenter = function() {
+          this.mouseoverElem.onmouseover();
+        };
+        layerPreview.onmouseout = function() {
+          this.mouseoverElem.onmouseout();
+        };
+      }
+    }
+
+    var layerDisplayItems = getDisplayItemForLayer(displayList);
+    for (let i = 0; i < layerDisplayItems.length; i++) {
+      var displayItem = layerDisplayItems[i];
+      var displayElem = createElement("div", {
+        className: "layerObjectDescription",
+        textContent: "            " + trim(displayItem.line),
+        style: {
+          whiteSpace: "pre",
+        },
+        displayItem,
+        layerViewport,
+        onmouseover() {
+          if (this.diPreview) {
+            this.diPreview.classList.add("displayHover");
+
+            var description = "";
+            if (this.displayItem.contentDescriptor) {
+              description += "Content: " + this.displayItem.contentDescriptor;
+            } else {
+              description += "Content: Unknown";
+            }
+            description +=
+              "<br>Item: " +
+              this.displayItem.name +
+              " (" +
+              this.displayItem.address +
+              ")";
+            description +=
+              "<br>Layer: " + root.name + " (" + root.address + ")";
+            if (this.displayItem.frame) {
+              description += "<br>Frame: " + this.displayItem.frame;
+            }
+            if (this.displayItem.layerBounds) {
+              description +=
+                "<br>Bounds: [" +
+                toFixed(this.displayItem.layerBounds[0] / 60, 2) +
+                ", " +
+                toFixed(this.displayItem.layerBounds[1] / 60, 2) +
+                ", " +
+                toFixed(this.displayItem.layerBounds[2] / 60, 2) +
+                ", " +
+                toFixed(this.displayItem.layerBounds[3] / 60, 2) +
+                "] (CSS Pixels)";
+            }
+            if (this.displayItem.z) {
+              description += "<br>Z: " + this.displayItem.z;
+            }
+            // At the end
+            if (this.displayItem.rest) {
+              description += "<br>" + this.displayItem.rest;
+            }
+
+            var box = this.diPreview.getBoundingClientRect();
+            this.diPreview.tooltip = createElement("div", {
+              className: "csstooltip",
+              innerHTML: description,
+              style: {
+                top:
+                  Math.min(
+                    box.bottom,
+                    document.documentElement.clientHeight - 150
+                  ) + "px",
+                left: box.left + "px",
+              },
+            });
+
+            document.body.appendChild(this.diPreview.tooltip);
+          }
+        },
+        onmouseout() {
+          if (this.diPreview) {
+            this.diPreview.classList.remove("displayHover");
+            document.body.removeChild(this.diPreview.tooltip);
+          }
+        },
+      });
+
+      icon = createElement("img", {
+        style: {
+          width: "12px",
+          height: "12px",
+          marginLeft: "4px",
+          marginRight: "4px",
+        },
+      });
+      displayElem.insertBefore(icon, displayElem.firstChild);
+      pane.appendChild(displayElem);
+      // bounds doesn't adjust for within the layer. It's not a bad fallback but
+      // will have the wrong offset
+      let rect2d = displayItem.layerBounds || displayItem.bounds;
+      if (rect2d) {
+        // This doesn't place them corectly
+        var appUnitsToPixels = 60 / contentScale;
+        let diPreview = createElement("div", {
+          id: "displayitem_" + displayItem.content + "_" + displayItem.address,
+          className: "layerPreview",
+          style: {
+            position: "absolute",
+            left: rect2d[0] / appUnitsToPixels + "px",
+            top: rect2d[1] / appUnitsToPixels + "px",
+            width: rect2d[2] / appUnitsToPixels + "px",
+            height: rect2d[3] / appUnitsToPixels + "px",
+            border: "solid 1px gray",
+            pointerEvents: "auto",
+          },
+          displayElem,
+          onmouseover() {
+            this.displayElem.onmouseover();
+          },
+          onmouseout() {
+            this.displayElem.onmouseout();
+          },
+        });
+
+        layerViewport.appendChild(diPreview);
+        displayElem.diPreview = diPreview;
+      }
+    }
+  }
+
+  for (var i = 0; i < root.children.length; i++) {
+    populateLayers(
+      root.children[i],
+      displayList,
+      pane,
+      previewParent,
+      hasSeenRoot,
+      contentScale,
+      rootPreviewParent
+    );
+  }
+}
+
+// This function takes a stdout snippet and finds the frames
+function parseMultiLineDump(log) {
+  var container = createElement("div", {
+    style: {
+      height: "100%",
+      position: "relative",
+    },
+  });
+
+  var layerManagerFirstLine = "[a-zA-Z]*LayerManager \\(.*$\n";
+  var nextLineStartWithSpace = "([ \\t].*$\n)*";
+  var layersRegex = "(" + layerManagerFirstLine + nextLineStartWithSpace + ")";
+
+  var startLine = "Painting --- after optimization:\n";
+  var endLine = "Painting --- layer tree:";
+  var displayListRegex = "(" + startLine + "(.*\n)*?" + endLine + ")";
+
+  var regex = new RegExp(layersRegex + "|" + displayListRegex, "gm");
+  var matches = log.match(regex);
+  console.log(matches);
+  window.matches = matches;
+
+  var matchList = createElement("span", {
+    style: {
+      height: "95%",
+      width: "10%",
+      position: "relative",
+      border: "solid black 2px",
+      display: "inline-block",
+      float: "left",
+      overflow: "auto",
+    },
+  });
+  container.appendChild(matchList);
+  var contents = createElement("span", {
+    style: {
+      height: "95%",
+      width: "88%",
+      display: "inline-block",
+    },
+    textContent: "Click on a frame on the left to view the layer tree",
+  });
+  container.appendChild(contents);
+
+  var lastDisplayList = null;
+  var frameID = 1;
+  for (let i = 0; i < matches.length; i++) {
+    var currMatch = matches[i];
+
+    if (currMatch.indexOf(startLine) == 0) {
+      // Display list match
+      var matchLines = matches[i].split("\n");
+      lastDisplayList = parseDisplayList(matchLines);
+    } else {
+      // Layer tree match:
+      let displayList = lastDisplayList;
+      lastDisplayList = null;
+      var currFrameDiv = createElement("a", {
+        style: {
+          padding: "3px",
+          display: "block",
+        },
+        href: "#",
+        textContent: "LayerTree " + frameID++,
+        onclick() {
+          contents.innerHTML = "";
+          var matchLines = matches[i].split("\n");
+          var dumpDiv = parseDump(matchLines, displayList);
+          contents.appendChild(dumpDiv);
+        },
+      });
+      matchList.appendChild(currFrameDiv);
+    }
+  }
+
+  return container;
+}
+
+function parseDump(log, displayList, compositeTitle, compositeTime) {
+  compositeTitle |= "";
+  compositeTime |= 0;
+
+  var container = createElement("div", {
+    style: {
+      background: "white",
+      height: "100%",
+      position: "relative",
+    },
+  });
+
+  if (compositeTitle == null && compositeTime == null) {
+    var titleDiv = createElement("div", {
+      className: "treeColumnHeader",
+      style: {
+        width: "100%",
+      },
+      textContent:
+        compositeTitle +
+        (compositeTitle ? " (near " + compositeTime.toFixed(0) + " ms)" : ""),
+    });
+    container.appendChild(titleDiv);
+  }
+
+  var mainDiv = createElement("div", {
+    style: {
+      position: "absolute",
+      top: "16px",
+      left: "0px",
+      right: "0px",
+      bottom: "0px",
+    },
+  });
+  container.appendChild(mainDiv);
+
+  var layerListPane = createElement("div", {
+    style: {
+      cssFloat: "left",
+      height: "100%",
+      width: "300px",
+      overflowY: "scroll",
+    },
+  });
+  mainDiv.appendChild(layerListPane);
+
+  var previewDiv = createElement("div", {
+    style: {
+      position: "absolute",
+      left: "300px",
+      right: "0px",
+      top: "0px",
+      bottom: "0px",
+      overflow: "auto",
+    },
+  });
+  mainDiv.appendChild(previewDiv);
+
+  var root = parseLayers(log);
+  populateLayers(root, displayList, layerListPane, previewDiv);
+  return container;
+}
diff --git a/gfx/layers/layerviewer/noise.png b/gfx/layers/layerviewer/noise.png
new file mode 100644
index 0000000000..01d340aaa9
--- /dev/null
+++ b/gfx/layers/layerviewer/noise.png
diff --git a/gfx/layers/layerviewer/show.png b/gfx/layers/layerviewer/show.png
new file mode 100644
index 0000000000..7038b660c8
--- /dev/null
+++ b/gfx/layers/layerviewer/show.png
diff --git a/gfx/layers/layerviewer/tree.css b/gfx/layers/layerviewer/tree.css
new file mode 100644
index 0000000000..18e5881c00
--- /dev/null
+++ b/gfx/layers/layerviewer/tree.css
@@ -0,0 +1,39 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+html, body {
+  height: 100%;
+  overflow: hidden;
+}
+.layerObjectDescription:hover {
+  background-color: #E8E8E8;
+}
+
+.layerHover > .layerPreview::after {
+  position: absolute;
+  top: 0; right: 0; bottom: 0; left: 0;
+  background-color: inherit;
+  content: "";
+  background-color: rgba(0,0,0,0.2);
+  box-shadow: -2px 2px 0 #FFF;
+}
+
+@keyframes layerHoverAnimation {
+  0% { transform: scale(1); }
+  50% { transform: scale(1.2); }
+  100% { transform: scale(1); }
+}
+
+.displayHover {
+  background: rgba(0, 128, 0, 0.8);
+}
+
+.layerHover > .layerPreview {
+  animation: layerHoverAnimation 200ms;
+  animation-transform-origin: 50% 50%;
+  background: gold !important;
+  box-shadow: 10px 10px 5px #888888;
+  border-color: blue !important;
+  z-index: 10;
+}