[Mac] Switch from NSObject categories to forward declarations for Touch Bar support.

ui/base/cocoa/touch_bar_forward_declarations.h

Index: ui/base/cocoa/touch_bar_forward_declarations.h
diff --git a/ui/base/cocoa/touch_bar_forward_declarations.h b/ui/base/cocoa/touch_bar_forward_declarations.h
index 54c68ae534ba473664f61d8cdc69de1982752224..52280c23ef0bdd6ab2400edf89bc0003b5f0d78a 100644
--- a/ui/base/cocoa/touch_bar_forward_declarations.h
+++ b/ui/base/cocoa/touch_bar_forward_declarations.h
@@ -11,38 +11,88 @@
 
 #if !defined(MAC_OS_X_VERSION_10_12_1)
 
-// The TouchBar classes do not exist at all without the 10.12.1 SDK. When
-// compiling with older SDKs, pretend they are NSObject and add categories to
-// NSObject to expose the methods.
-// To alloc one of these classes, use -[NSClassFromString(@"..") alloc].
+#pragma clang assume_nonnull begin

[tapted, 2016/11/30 23:29:27]

I think this is OK since we're replicating a system header and want to reduce
the likelihood that we let stuff through the CQ that will break when compiling
against the authentic 10.12.1 SDK  (but if you're curious there's some active
discussion around whether we should use audited regions like this for new code
at http://go/uzjld  )

 
-// Incomplete. Add more as necessary.
+@class NSTouchBar, NSTouchBarItem;
+@protocol NSTouchBarDelegate;
+
+typedef float NSTouchBarItemPriority;
+static const NSTouchBarItemPriority NSTouchBarItemPriorityHigh = 1000;
+static const NSTouchBarItemPriority NSTouchBarItemPriorityNormal = 0;
+static const NSTouchBarItemPriority NSTouchBarItemPriorityLow = -1000;
 
-typedef NSObject NSCustomTouchBarItem;
-typedef NSObject NSGroupTouchBarItem;
-typedef NSObject NSTouchBar;
-typedef NSObject NSTouchBarItem;
 typedef NSString* NSTouchBarItemIdentifier;
+typedef NSString* NSTouchBarCustomizationIdentifier;
+
+@interface NSTouchBar : NSObject<NSCoding>
+
+- (instancetype)init NS_DESIGNATED_INITIALIZER;

[tapted, 2016/11/30 23:29:27]

Internet suggests NS_DESIGNATED_INITIALIZER is XCode 6, but I'm not sure on the
SDK. https://www.chromium.org/developers/design-documents/mac-xib-files suggests
we still use XCode 5 in some places. But I _think_ this is OK now.
NS_DESIGNATED_INITIALIZER is used a lot on a lot of ios code, but
image_capture_device_manager_unittest.mm is the only occurence I could find for
MacOS code. (and it looks like official builders are happy with that).

My 10.10 SDK's NSObjCRuntime.h has this defined in any case.

+- (nullable instancetype)initWithCoder:(NSCoder*)aDecoder
+    NS_DESIGNATED_INITIALIZER;
+
+@property(copy, nullable)
+    NSTouchBarCustomizationIdentifier customizationIdentifier;
+@property(copy) NSArray* customizationAllowedItemIdentifiers;
+@property(copy) NSArray* customizationRequiredItemIdentifiers;
+@property(copy) NSArray* defaultItemIdentifiers;
+@property(copy, readonly) NSArray* itemIdentifiers;
+@property(copy, nullable) NSTouchBarItemIdentifier principalItemIdentifier;
+@property(copy) NSSet* templateItems;
+@property(nullable, weak) id<NSTouchBarDelegate> delegate;
+
+- (nullable __kindof NSTouchBarItem*)itemForIdentifier:

[tapted, 2016/11/30 23:29:27]

I think __kindof is Xcode 7 (10.11 SDK). But hopefully this is a compiler
intrinsic so isn't dependent on the SDK we link against. (i.e. the 10.10 SDK
won't have any generics and might get confused :/)

+    (NSTouchBarItemIdentifier)identifier;
+
+@property(readonly, getter=isVisible) BOOL visible;
 
-@protocol NSTouchBarDelegate<NSObject>
 @end
 
-@interface NSObject (FakeNSCustomTouchBarItem)
-@property(readwrite, strong) NSView* view;
+@interface NSTouchBarItem : NSObject<NSCoding>
+
+- (instancetype)initWithIdentifier:(NSTouchBarItemIdentifier)identifier
+    NS_DESIGNATED_INITIALIZER;
+- (nullable instancetype)initWithCoder:(NSCoder*)coder
+    NS_DESIGNATED_INITIALIZER;
+- (instancetype)init NS_UNAVAILABLE;
+
+@property(readonly, copy) NSTouchBarItemIdentifier identifier;
+@property NSTouchBarItemPriority visibilityPriority;
+@property(readonly, nullable) NSView* view;
+@property(readonly, nullable) NSViewController* viewController;
+@property(readonly, copy) NSString* customizationLabel;
+@property(readonly, getter=isVisible) BOOL visible;
+
 @end
 
-@interface NSObject (FakeNSGroupTouchBarItem)
+@interface NSGroupTouchBarItem : NSTouchBarItem
+
 + (NSGroupTouchBarItem*)groupItemWithIdentifier:
                             (NSTouchBarItemIdentifier)identifier
                                           items:(NSArray*)items;
+
+@property(strong) NSTouchBar* groupTouchBar;
+@property(readwrite, copy, null_resettable) NSString* customizationLabel;
+
 @end
 
-@interface NSObject (FakeNSTouchBar)
-@property(copy) NSArray* defaultItemIdentifiers;
-@property(copy) NSTouchBarItemIdentifier principalItemIdentifier;
-@property(weak) id<NSTouchBarDelegate> delegate;
+@interface NSCustomTouchBarItem : NSTouchBarItem
+
+@property(readwrite, strong) __kindof NSView* view;
+@property(readwrite, strong, nullable)
+    __kindof NSViewController* viewController;
+@property(readwrite, copy, null_resettable) NSString* customizationLabel;
+
 @end
 
+@protocol NSTouchBarDelegate<NSObject>
+
+@optional
+- (nullable NSTouchBarItem*)touchBar:(NSTouchBar*)touchBar
+               makeItemForIdentifier:(NSTouchBarItemIdentifier)identifier;
+@end
+
+#pragma clang assume_nonnull end
+
 #elif MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12_1
 
 // When compiling against the 10.12.1 SDK or later, just provide forward