Move add collection pane to React (#486)

* Move add collection pane to React

* Add feature flag

* fix unit tests

* FIx merge conflicts and address comments

* Resolve merge conflicts

* Address comments

* Fix e2e test failure

* Update test snapshots

* Update test snapshots

src/Explorer/Controls/CollapsiblePanel/CollapsibleSectionComponent.test.tsx

@@ -6,6 +6,7 @@ describe("CollapsibleSectionComponent", () => {
   it("renders", () => {
     const props: CollapsibleSectionProps = {
       title: "Sample title",
+      isExpandedByDefault: true,
     };
 
     const wrapper = shallow(<CollapsibleSectionComponent {...props} />);

src/Explorer/Controls/CollapsiblePanel/CollapsibleSectionComponent.tsx

@@ -1,9 +1,10 @@
 import { Icon, Label, Stack } from "office-ui-fabric-react";
 import * as React from "react";
-import { accordionIconStyles, accordionStackTokens } from "../Settings/SettingsRenderUtils";
+import { accordionStackTokens } from "../Settings/SettingsRenderUtils";
 
 export interface CollapsibleSectionProps {
   title: string;
+  isExpandedByDefault: boolean;
 }
 
 export interface CollapsibleSectionState {
@@ -14,7 +15,7 @@ export class CollapsibleSectionComponent extends React.Component<CollapsibleSect
   constructor(props: CollapsibleSectionProps) {
     super(props);
     this.state = {
-      isExpanded: true,
+      isExpanded: this.props.isExpandedByDefault,
     };
   }
 
@@ -25,8 +26,14 @@ export class CollapsibleSectionComponent extends React.Component<CollapsibleSect
   public render(): JSX.Element {
     return (
       <>
-        <Stack className="collapsibleSection" horizontal tokens={accordionStackTokens} onClick={this.toggleCollapsed}>
-          <Icon iconName={this.state.isExpanded ? "ChevronDown" : "ChevronRight"} styles={accordionIconStyles} />
+        <Stack
+          className="collapsibleSection"
+          horizontal
+          verticalAlign="center"
+          tokens={accordionStackTokens}
+          onClick={this.toggleCollapsed}
+        >
+          <Icon iconName={this.state.isExpanded ? "ChevronDown" : "ChevronRight"} />
           <Label>{this.props.title}</Label>
         </Stack>
         {this.state.isExpanded && this.props.children}

src/Explorer/Controls/CollapsiblePanel/__snapshots__/CollapsibleSectionComponent.test.tsx.snap

@@ -11,16 +11,10 @@ exports[`CollapsibleSectionComponent renders 1`] = `
         "childrenGap": 10,
       }
     }
+    verticalAlign="center"
   >
     <Icon
       iconName="ChevronDown"
-      styles={
-        Object {
-          "root": Object {
-            "paddingTop": 7,
-          },
-        }
-      }
     />
     <StyledLabelBase>
       Sample title