Revert "Make all MacViews windows potentially draggable."

This reverts commit 330fc4a1.

Reason for revert: speculative revert to fix views_unittests (https://bugs.chromium.org/p/chromium/issues/detail?id=859829).

Original change's description:
> 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}

TBR=avi@chromium.org,sdy@chromium.org

Change-Id: Ic1e718a03d272c2c1b4646ead018ad776d03fd18
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 849983,859829
Reviewed-on: https://chromium-review.googlesource.com/1124299
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572161}

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

@@ -15,13 +15,19 @@
 
 @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
 
-@interface NSThemeFrame (PrivateAPI)
+// Weak lets Chrome launch even if a future macOS doesn't have NSThemeFrame.
+WEAK_IMPORT_ATTRIBUTE
+@interface NSThemeFrame : NSView
 - (CGFloat)_titlebarHeight;
 @end
 
-@interface BrowserWindowFrame : NativeWidgetMacNSWindowTitledFrame
+@interface BrowserWindowFrame : NSThemeFrame
 @end
 
 @implementation BrowserWindowFrame
@@ -72,6 +78,20 @@
   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
@@ -87,6 +107,13 @@
   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

@@ -6,13 +6,31 @@
 
 @interface NSWindow (PrivateAPI)
 + (Class)frameViewClassForStyleMask:(NSUInteger)windowStyle;
+- (void)beginWindowDragWithEvent:(NSEvent*)event
+    NS_DEPRECATED_MAC(10_10, 10_11, "Use performWindowDragWithEvent: instead.");
 @end
 
-@interface NativeWidgetMacFramelessNSWindowFrame
-    : NativeWidgetMacNSWindowTitledFrame
+// Weak lets Chrome launch even if a future macOS doesn't have NSThemeFrame.
+WEAK_IMPORT_ATTRIBUTE
+@interface NSThemeFrame : NSView
+@end
+
+@interface NativeWidgetMacFramelessNSWindowFrame : NSThemeFrame
 @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;
 }
@@ -27,4 +45,8 @@
   return [super frameViewClassForStyleMask:windowStyle];
 }
 
+- (BOOL)_usesCustomDrawing {
+  return NO;
+}
+
 @end

ui/views/cocoa/native_widget_mac_nswindow.h

@@ -12,24 +12,6 @@
 
 @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

@@ -15,12 +15,7 @@
 #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 ()
@@ -34,38 +29,6 @@
 - (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_;
@@ -136,17 +99,6 @@
 
 // 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;
@@ -154,13 +106,6 @@
   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