Add FlutterMutatorViewTest

Author: knopp

ci/licenses_golden/licenses_flutter

@@ -2672,6 +2672,7 @@ ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMou
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorView.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorView.mm + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorViewTest.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMac.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMac.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMacTest.mm + ../../../flutter/LICENSE
@@ -5168,6 +5169,7 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMouse
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorView.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorView.mm
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorViewTest.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMac.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMac.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMacTest.mm

shell/platform/darwin/macos/BUILD.gn

@@ -174,6 +174,7 @@ executable("flutter_desktop_darwin_unittests") {
     "framework/Source/FlutterEngineTestUtils.mm",
     "framework/Source/FlutterKeyboardManagerTest.mm",
     "framework/Source/FlutterMenuPluginTest.mm",
+    "framework/Source/FlutterMutatorViewTest.mm",
     "framework/Source/FlutterPlatformNodeDelegateMacTest.mm",
     "framework/Source/FlutterPlatformViewControllerTest.mm",
     "framework/Source/FlutterRendererTest.mm",

shell/platform/darwin/macos/framework/Source/FlutterMutatorView.h

@@ -22,3 +22,10 @@
 - (void)applyFlutterLayer:(nonnull const FlutterLayer*)layer;
 
 @end
+
+@interface FlutterMutatorView (Private)
+
+@property(readonly, nonatomic, nonnull) NSMutableArray<NSView*>* pathClipViews;
+@property(readonly, nonatomic, nullable) NSView* platformViewContainer;
+
+@end

shell/platform/darwin/macos/framework/Source/FlutterMutatorView.mm

@@ -194,6 +194,14 @@ - (NSView*)platformView {
   return _platformView;
 }
 
+- (NSMutableArray*)pathClipViews {
+  return _pathClipViews;
+}
+
+- (NSView*)platformViewContainer {
+  return _platformViewContainer;
+}
+
 - (instancetype)initWithPlatformView:(NSView*)platformView {
   if (self = [super initWithFrame:NSZeroRect]) {
     _platformView = platformView;
@@ -215,7 +223,7 @@ - (BOOL)isFlipped {
 /// If clipping to path is needed, CAShapeLayer(s) will be used as mask.
 /// Clipping to round rect only clips to path if round corners are intersected.
 - (void)applyFlutterLayer:(const FlutterLayer*)layer {
-  CGFloat scale = self.superview.layer.contentsScale;
+  CGFloat scale = self.superview != nil ? self.superview.layer.contentsScale : 1.0;
 
   // Initial transform to compensate for scale factor. This is needed because all
   // cocoa coordinates are logical but Flutter will send the physical to logical