Make all MacViews windows potentially draggable.

This fixes the PiP window not being draggable on Mac.

Bug: 849983
Change-Id: I1b0f503de1a1f154f23afd1870943a6b7009be75
Reviewed-on: https://chromium-review.googlesource.com/1121145
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572038}

chrome/browser/ui/views/frame/browser_native_widget_window_mac.mm

@@ -15,19 +15,13 @@
 
 @interface NSWindow (PrivateAPI)
 + (Class)frameViewClassForStyleMask:(NSUInteger)windowStyle;
-
-// Available in later point releases of 10.10. On 10.11+, use the public
-// -performWindowDragWithEvent: instead.
-- (void)beginWindowDragWithEvent:(NSEvent*)event;
 @end
 
-// Weak lets Chrome launch even if a future macOS doesn't have NSThemeFrame.
-WEAK_IMPORT_ATTRIBUTE
-@interface NSThemeFrame : NSView
+@interface NSThemeFrame (PrivateAPI)
 - (CGFloat)_titlebarHeight;
 @end
 
-@interface BrowserWindowFrame : NSThemeFrame
+@interface BrowserWindowFrame : NativeWidgetMacNSWindowTitledFrame
 @end
 
 @implementation BrowserWindowFrame
@@ -78,20 +72,6 @@ WEAK_IMPORT_ATTRIBUTE
   return NSZeroRect;
 }
 
-// Lets the window be dragged by its title bar on 10.11 and older.
-- (void)mouseDown:(NSEvent*)event {
-  if (@available(macOS 10.12, *))
-    ;  // Not needed on 10.12 and up.
-  else if (@available(macOS 10.11, *))
-    [self.window performWindowDragWithEvent:event];
-  else if ([self.window
-               respondsToSelector:@selector(beginWindowDragWithEvent:)])
-    [self.window beginWindowDragWithEvent:event];
-  else
-    NOTREACHED();
-  [super mouseDown:event];
-}
-
 @end
 
 @implementation BrowserNativeWidgetWindow
@@ -107,13 +87,6 @@ WEAK_IMPORT_ATTRIBUTE
   return [super frameViewClassForStyleMask:windowStyle];
 }
 
-// The base implementation returns YES if the window's frame view is a custom
-// class, which causes undesirable changes in behavior. AppKit NSWindow
-// subclasses are known to override it and return NO.
-- (BOOL)_usesCustomDrawing {
-  return NO;
-}
-
 // Handle "Move focus to the window toolbar" configured in System Preferences ->
 // Keyboard -> Shortcuts -> Keyboard. Usually Ctrl+F5. The argument (|unknown|)
 // tends to just be nil.

chrome/browser/ui/views/frame/native_widget_mac_frameless_nswindow.mm

@@ -6,31 +6,13 @@
 
 @interface NSWindow (PrivateAPI)
 + (Class)frameViewClassForStyleMask:(NSUInteger)windowStyle;
-- (void)beginWindowDragWithEvent:(NSEvent*)event
-    NS_DEPRECATED_MAC(10_10, 10_11, "Use performWindowDragWithEvent: instead.");
 @end
 
-// Weak lets Chrome launch even if a future macOS doesn't have NSThemeFrame.
-WEAK_IMPORT_ATTRIBUTE
-@interface NSThemeFrame : NSView
-@end
-
-@interface NativeWidgetMacFramelessNSWindowFrame : NSThemeFrame
+@interface NativeWidgetMacFramelessNSWindowFrame
+    : NativeWidgetMacNSWindowTitledFrame
 @end
 
 @implementation NativeWidgetMacFramelessNSWindowFrame
-
-// If a mouseDown: falls through to the frame view, turn it into a window drag.
-- (void)mouseDown:(NSEvent*)event {
-  if (@available(macOS 10.11, *))
-    [self.window performWindowDragWithEvent:event];
-  else if (@available(macOS 10.10, *))
-    [self.window beginWindowDragWithEvent:event];
-  else
-    NOTREACHED();
-  [super mouseDown:event];
-}
-
 - (BOOL)_hidingTitlebar {
   return YES;
 }
@@ -45,8 +27,4 @@ WEAK_IMPORT_ATTRIBUTE
   return [super frameViewClassForStyleMask:windowStyle];
 }
 
-- (BOOL)_usesCustomDrawing {
-  return NO;
-}
-
 @end

ui/views/cocoa/native_widget_mac_nswindow.h

@@ -12,6 +12,24 @@
 
 @protocol WindowTouchBarDelegate;
 
+// Weak lets Chrome launch even if a future macOS doesn't have the below classes
+
+WEAK_IMPORT_ATTRIBUTE
+@interface NSNextStepFrame : NSView
+@end
+
+WEAK_IMPORT_ATTRIBUTE
+@interface NSThemeFrame : NSView
+@end
+
+VIEWS_EXPORT
+@interface NativeWidgetMacNSWindowBorderlessFrame : NSNextStepFrame
+@end
+
+VIEWS_EXPORT
+@interface NativeWidgetMacNSWindowTitledFrame : NSThemeFrame
+@end
+
 // The NSWindow used by BridgedNativeWidget. Provides hooks into AppKit that
 // can only be accomplished by overriding methods.
 VIEWS_EXPORT

ui/views/cocoa/native_widget_mac_nswindow.mm

@@ -15,7 +15,12 @@
 #include "ui/views/widget/widget_delegate.h"
 
 @interface NSWindow (Private)
++ (Class)frameViewClassForStyleMask:(NSWindowStyleMask)windowStyle;
 - (BOOL)hasKeyAppearance;
+
+// Available in later point releases of 10.10. On 10.11+, use the public
+// -performWindowDragWithEvent: instead.
+- (void)beginWindowDragWithEvent:(NSEvent*)event;
 @end
 
 @interface NativeWidgetMacNSWindow ()
@@ -29,6 +34,38 @@
 - (BOOL)_isTitleHidden;
 @end
 
+// Use this category to implement mouseDown: on multiple frame view classes
+// with different superclasses.
+@interface NSView (CRFrameViewAdditions)
+- (void)cr_mouseDownOnFrameView:(NSEvent*)event;
+@end
+
+@implementation NSView (CRFrameViewAdditions)
+// If a mouseDown: falls through to the frame view, turn it into a window drag.
+- (void)cr_mouseDownOnFrameView:(NSEvent*)event {
+  if (@available(macOS 10.11, *))
+    return [self.window performWindowDragWithEvent:event];
+  else if ([self.window
+               respondsToSelector:@selector(beginWindowDragWithEvent:)])
+    return [self.window beginWindowDragWithEvent:event];
+  else
+    NOTREACHED();
+  [super mouseDown:event];
+}
+@end
+
+@implementation NativeWidgetMacNSWindowTitledFrame
+- (void)mouseDown:(NSEvent*)event {
+  [self cr_mouseDownOnFrameView:event];
+}
+@end
+
+@implementation NativeWidgetMacNSWindowBorderlessFrame
+- (void)mouseDown:(NSEvent*)event {
+  [self cr_mouseDownOnFrameView:event];
+}
+@end
+
 @implementation NativeWidgetMacNSWindow {
  @private
   base::scoped_nsobject<CommandDispatcher> commandDispatcher_;
@@ -99,6 +136,17 @@
 
 // NSWindow overrides.
 
++ (Class)frameViewClassForStyleMask:(NSWindowStyleMask)windowStyle {
+  if (windowStyle & NSWindowStyleMaskTitled) {
+    if (Class customFrame = [NativeWidgetMacNSWindowTitledFrame class])
+      return customFrame;
+  } else if (Class customFrame =
+                 [NativeWidgetMacNSWindowBorderlessFrame class]) {
+    return customFrame;
+  }
+  return [super frameViewClassForStyleMask:windowStyle];
+}
+
 - (BOOL)_isTitleHidden {
   if (![self delegate])
     return NO;
@@ -106,6 +154,13 @@
   return ![self viewsWidget]->widget_delegate()->ShouldShowWindowTitle();
 }
 
+// The base implementation returns YES if the window's frame view is a custom
+// class, which causes undesirable changes in behavior. AppKit NSWindow
+// subclasses are known to override it and return NO.
+- (BOOL)_usesCustomDrawing {
+  return NO;
+}
+
 // Ignore [super canBecome{Key,Main}Window]. The default is NO for windows with
 // NSBorderlessWindowMask, which is not the desired behavior.
 // Note these can be called via -[NSWindow close] while the widget is being torn