DevTools: autocomplete non-SVG properties for SVG elements

This patch changes StylesSidebarPane autocomplete for property names in
the following maner:
- for regular nodes, only regular CSS properties are autocompleted
- for SVG nodes, both CSS and SVG properties are autocompleted

BUG=721998
R=dgozman

Change-Id: Ie06307d62a1b9685f0bf998b5b2714c47e3d5ee8
Reviewed-on: https://chromium-review.googlesource.com/820647Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523269}

third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js

@@ -2562,8 +2562,8 @@ Elements.StylePropertyTreeElement = class extends UI.TreeElement {
     var cssCompletions = [];
     if (isEditingName) {
       cssCompletions = SDK.cssMetadata().allProperties();
-      cssCompletions =
-          cssCompletions.filter(property => SDK.cssMetadata().isSVGProperty(property) === this.node().isSVGNode());
+      if (!this.node().isSVGNode())
+        cssCompletions = cssCompletions.filter(property => !SDK.cssMetadata().isSVGProperty(property));
     } else {
       cssCompletions = SDK.cssMetadata().propertyValues(this.nameElement.textContent);
     }