🐛 Set the device selector component to opaque during its creation (flutter#8471)

Fixes flutter#8439
Fixes flutter#7972

This is inspired by
[StackOverflow](https://stackoverflow.com/questions/13939176/making-jcombobox-transparent),
Claude Sonnet 4, and Gemini 2.5 Pro.

Before:
<img width="736" height="40" alt="image"
src="https://github.com/user-attachments/assets/90afd256-19d9-4023-8401-5099d3e2a488"
/>

After:
<img width="736" height="40" alt="image"
src="https://github.com/user-attachments/assets/05b5d538-aa4d-4c86-b10d-2aba7c596dd3"
/>

Author: AlexV525

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 - Resolved a "Slow operations are prohibited on EDT" exception on Flutter Project creation (#8446, #8447, #8448)
 - Made dev release daily instead of weekly
+- Set the device selector component to opaque during its creation to avoid an unexpected background color (#8471)
 
 ## 87.1.0
 

src/io/flutter/actions/DeviceSelectorAction.java

@@ -18,6 +18,7 @@
 import com.intellij.openapi.util.Condition;
 import com.intellij.openapi.util.Key;
 import com.intellij.openapi.util.SystemInfo;
+import com.intellij.ui.JBColor;
 import com.intellij.util.ModalityUiUtil;
 import icons.FlutterIcons;
 import io.flutter.FlutterBundle;
@@ -29,6 +30,7 @@
 import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
+import java.awt.Component;
 import java.util.*;
 
 public class DeviceSelectorAction extends ComboBoxAction implements DumbAware {
@@ -45,6 +47,39 @@ public class DeviceSelectorAction extends ComboBoxAction implements DumbAware {
     return ActionUpdateThread.BGT;
   }
 
+  @Override
+  public @NotNull JComponent createCustomComponent(@NotNull Presentation presentation, @NotNull String place) {
+    final JComponent component = super.createCustomComponent(presentation, place);
+    // Set component to be transparent to match other toolbar actions
+    component.setOpaque(false);
+    // Update child components.
+    updateComponentChildrenStyles(component);
+    return component;
+  }
+
+  private void updateComponentChildrenStyles(@NotNull JComponent parent) {
+    final @Nullable Component[] children = parent.getComponents();
+    if (children == null) {
+      return;
+    }
+
+    for (Component child : children) {
+      if (child instanceof JComponent jComponent) {
+        jComponent.setOpaque(false);
+
+        if (child instanceof JButton jButton) {
+          jButton.setBorderPainted(false);
+          jButton.setRolloverEnabled(true);
+          // Make sure the button uses correct background & foreground.
+          jButton.setBackground(JBColor.background());
+          jButton.setForeground(JBColor.foreground());
+        }
+
+        updateComponentChildrenStyles(jComponent);
+      }
+    }
+  }
+
   @Override
   protected @NotNull DefaultActionGroup createPopupActionGroup(@NotNull JComponent button, @NotNull DataContext dataContext) {
     final DefaultActionGroup group = new DefaultActionGroup();