Revert "Fix tabs briefly animating too wide after finishing closing some tabs"

app/renderer/components/tabs/tab.js

@@ -295,6 +295,29 @@ class Tab extends React.Component {
     return props
   }
 
+  componentWillReceiveProps (nextProps) {
+    if (this.props.tabWidth && !nextProps.tabWidth) {
+      // remember the width so we can transition from it
+      this.originalWidth = this.elementRef.getBoundingClientRect().width
+    }
+  }
+
+  componentDidUpdate (prevProps) {
+    if (prevProps.tabWidth && !this.props.tabWidth) {
+      window.requestAnimationFrame(() => {
+        const newWidth = this.elementRef.getBoundingClientRect().width
+        this.elementRef.animate([
+          { flexBasis: `${this.originalWidth}px`, flexGrow: 0, flexShrink: 0 },
+          { flexBasis: `${newWidth}px`, flexGrow: 0, flexShrink: 0 }
+        ], {
+          duration: 250,
+          iterations: 1,
+          easing: 'ease-in-out'
+        })
+      })
+    }
+  }
+
   render () {
     // we don't want themeColor if tab is private
     const isThemed = !this.props.isPrivateTab && this.props.isActive && this.props.themeColor
@@ -311,17 +334,16 @@ class Tab extends React.Component {
         (this.isDraggingOverRight && !this.isDraggingOverSelf) && styles.tabArea_dragging_right,
         this.isDragging && styles.tabArea_isDragging,
         this.props.isPinnedTab && styles.tabArea_isPinned,
-        (this.props.partOfFullPageSet || !!this.props.tabWidth) && styles.tabArea_partOfFullPageSet,
-        this.props.tabWidth && styles.tabArea_forcedWidth
+        (this.props.partOfFullPageSet || !!this.props.tabWidth) && styles.tabArea_partOfFullPageSet
       )}
+      style={this.props.tabWidth ? { flex: `0 0 ${this.props.tabWidth}px` } : {}}
       onMouseMove={this.onMouseMove}
       onMouseEnter={this.onMouseEnter}
       onMouseLeave={this.onMouseLeave}
       data-test-id='tab-area'
       data-frame-key={this.props.frameKey}
       ref={elementRef => { this.elementRef = elementRef }}
-      style={this.props.tabWidth ? { '--tab-forced-width': `${this.props.tabWidth}px` } : { }}
-    >
+      >
       {
         this.props.isActive && this.props.notificationBarActive
           ? <NotificationBarCaret />
@@ -392,8 +414,8 @@ const styles = StyleSheet.create({
     verticalAlign: 'top',
     overflow: 'hidden',
     height: '-webkit-fill-available',
-    flex: '1 1 0',
-    transition: 'flex .45s ease',
+    flex: 1,
+
     // no-drag is applied to the button and tab area
     // ref: tabs__tabStrip__newTabButton on tabs.js
     WebkitAppRegion: 'no-drag',
@@ -425,11 +447,6 @@ const styles = StyleSheet.create({
     maxWidth: 'initial'
   },
 
-  tabArea_forcedWidth: {
-    flex: '0 0 var(--tab-forced-width)',
-    transitionDuration: '0s'
-  },
-
   tabArea__tab: {
     borderWidth: '0 1px 0 0',
     borderStyle: 'solid',