Use correct size for unattached canvases when building canvas filters

The equivalent bug for attached canvases was fixed in
http://crrev.com/370047, but unattached canvases were ignored
there.

BUG=561045

Review URL: https://codereview.chromium.org/1613193002

Cr-Commit-Position: refs/heads/master@{#370719}

third_party/WebKit/LayoutTests/fast/canvas/canvas-filter-width-height-off-screen-expected.html

+<svg style="display: block; width: 0; height: 0">
+  <defs>
+    <filter id="crop" primitiveUnits="objectBoundingBox">
+      <femerge x="0" y="0" width="50%" height="40%">
+        <femergenode in="SourceGraphic"></femergenode>
+      </femerge>
+    </filter>
+  </defs>
+</svg>
+<canvas id="canvas" width="100" height="100"></canvas>
+<script>
+var canvas = document.getElementById('canvas');
+var ctx = canvas.getContext('2d');
+ctx.filter = 'url(#crop)';
+ctx.fillStyle = '#0f0';
+ctx.fillRect(0, 0, 90, 90);
+</script>

third_party/WebKit/LayoutTests/fast/canvas/canvas-filter-width-height-off-screen.html

+<svg style="display: block; width: 0; height: 0">
+  <defs>
+    <filter id="crop" primitiveUnits="objectBoundingBox">
+      <femerge x="0" y="0" width="50%" height="40%">
+        <femergenode in="SourceGraphic"></femergenode>
+      </femerge>
+    </filter>
+  </defs>
+</svg>
+<script>
+var canvas = document.createElement('canvas');
+canvas.width = 100;
+canvas.height = 100;
+var ctx = canvas.getContext('2d');
+ctx.filter = 'url(#crop)';
+ctx.fillStyle = '#0f0';
+ctx.fillRect(0, 0, 90, 90);
+document.body.appendChild(canvas);
+</script>

third_party/WebKit/Source/core/layout/svg/ReferenceFilterBuilder.cpp

@@ -100,13 +100,11 @@ PassRefPtrWillBeRawPtr<Filter> ReferenceFilterBuilder::build(float zoom, Element
     SVGFilterElement& filterElement = toSVGFilterElement(*filter);
 
     FloatRect referenceBox;
-    if (element->inDocument() && element->layoutObject() && element->layoutObject()->enclosingLayer()) {
-        if (referenceBoxSize) {
-            referenceBox = FloatRect(FloatPoint(), *referenceBoxSize);
-        } else {
-            FloatSize size(element->layoutObject()->enclosingLayer()->physicalBoundingBoxIncludingReflectionAndStackingChildren(LayoutPoint()).size());
-            referenceBox = FloatRect(FloatPoint(), size);
-        }
+    if (referenceBoxSize) {
+        referenceBox = FloatRect(FloatPoint(), *referenceBoxSize);
+    } else if (element->inDocument() && element->layoutObject() && element->layoutObject()->enclosingLayer()) {
+        FloatSize size(element->layoutObject()->enclosingLayer()->physicalBoundingBoxIncludingReflectionAndStackingChildren(LayoutPoint()).size());
+        referenceBox = FloatRect(FloatPoint(), size);
     }
     referenceBox.scale(1.0f / zoom);
     FloatRect filterRegion = SVGLengthContext::resolveRectangle<SVGFilterElement>(&filterElement, filterElement.filterUnits()->currentValue()->enumValue(), referenceBox);