Include i420 buffers in Obj-C framework again.

These headers was lost in the cleanup CL for the Obj-C directories. This
puts them back in the framework headers.

Note that since the protocol and interface was split into two different
headers, and all public framework headers are put into a flat directory
structure, I had to rename the implementation files so they would not collide
in the framework header directory.

Bug: webrtc:9701
Change-Id: I42d4c1e02bdfa4e114575f527c4c42a19be8fb52
Reviewed-on: https://webrtc-review.googlesource.com/97330
Reviewed-by: Peter Hanspers <peterhanspers@webrtc.org>
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24539}

sdk/objc/api/video_frame_buffer/RTCNativeI420Buffer+Private.h

@@ -8,7 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import "RTCI420Buffer.h"
+#import "RTCNativeI420Buffer.h"
 
 #include "api/video/i420_buffer.h"
 

sdk/objc/api/video_frame_buffer/RTCNativeI420Buffer.h

@@ -10,14 +10,14 @@
 
 #import <AVFoundation/AVFoundation.h>
 
-#import "base/RTCI420Buffer.h"
-#import "base/RTCMacros.h"
+#import "RTCI420Buffer.h"
+#import "RTCMacros.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
 /** RTCI420Buffer implements the RTCI420Buffer protocol */
 RTC_EXPORT
-@interface RTCI420Buffer : NSObject <RTCI420Buffer>
+@interface RTCI420Buffer : NSObject<RTCI420Buffer>
 @end
 
 NS_ASSUME_NONNULL_END

sdk/objc/api/video_frame_buffer/RTCNativeI420Buffer.mm

@@ -8,7 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import "RTCI420Buffer+Private.h"
+#import "RTCNativeI420Buffer+Private.h"
 
 #include "api/video/i420_buffer.h"
 

sdk/objc/api/video_frame_buffer/RTCNativeMutableI420Buffer.h

@@ -10,15 +10,15 @@
 
 #import <AVFoundation/AVFoundation.h>
 
-#import "RTCI420Buffer.h"
-#import "base/RTCMacros.h"
-#import "base/RTCMutableI420Buffer.h"
+#import "RTCMacros.h"
+#import "RTCMutableI420Buffer.h"
+#import "RTCNativeI420Buffer.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
 /** Mutable version of RTCI420Buffer */
 RTC_EXPORT
-@interface RTCMutableI420Buffer : RTCI420Buffer <RTCMutableI420Buffer>
+@interface RTCMutableI420Buffer : RTCI420Buffer<RTCMutableI420Buffer>
 @end
 
 NS_ASSUME_NONNULL_END

sdk/objc/api/video_frame_buffer/RTCNativeMutableI420Buffer.mm

@@ -8,9 +8,9 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import "RTCMutableI420Buffer.h"
+#import "RTCNativeMutableI420Buffer.h"
 
-#import "RTCI420Buffer+Private.h"
+#import "RTCNativeI420Buffer+Private.h"
 
 #include "api/video/i420_buffer.h"